xref: /frameworks/base/media/libstagefright/MPEG4Extractor.cpp

/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#define LOG_TAG "MPEG4Extractor"
#include <utils/Log.h>

#include "include/MPEG4Extractor.h"
#include "include/SampleTable.h"

#include <arpa/inet.h>

#include <ctype.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include <media/stagefright/foundation/ADebug.h>
#include <media/stagefright/DataSource.h>
#include "include/ESDS.h"
#include <media/stagefright/MediaBuffer.h>
#include <media/stagefright/MediaBufferGroup.h>
#include <media/stagefright/MediaDefs.h>
#include <media/stagefright/MediaSource.h>
#include <media/stagefright/MetaData.h>
#include <media/stagefright/Utils.h>
#include <utils/String8.h>

namespace android {

class MPEG4Source : public MediaSource {
public:
    // Caller retains ownership of both "dataSource" and "sampleTable".
    MPEG4Source(const sp<MetaData> &format,
                const sp<DataSource> &dataSource,
                int32_t timeScale,
                const sp<SampleTable> &sampleTable);

    virtual status_t start(MetaData *params = NULL);
    virtual status_t stop();

    virtual sp<MetaData> getFormat();

    virtual status_t read(
            MediaBuffer **buffer, const ReadOptions *options = NULL);

protected:
    virtual ~MPEG4Source();

private:
    Mutex mLock;

    sp<MetaData> mFormat;
    sp<DataSource> mDataSource;
    int32_t mTimescale;
    sp<SampleTable> mSampleTable;
    uint32_t mCurrentSampleIndex;

    bool mIsAVC;
    size_t mNALLengthSize;

    bool mStarted;

    MediaBufferGroup *mGroup;

    MediaBuffer *mBuffer;

    bool mWantsNALFragments;

    uint8_t *mSrcBuffer;

    size_t parseNALSize(const uint8_t *data) const;

    MPEG4Source(const MPEG4Source &);
    MPEG4Source &operator=(const MPEG4Source &);
};

// This custom data source wraps an existing one and satisfies requests
// falling entirely within a cached range from the cache while forwarding
// all remaining requests to the wrapped datasource.
// This is used to cache the full sampletable metadata for a single track,
// possibly wrapping multiple times to cover all tracks, i.e.
// Each MPEG4DataSource caches the sampletable metadata for a single track.

struct MPEG4DataSource : public DataSource {
    MPEG4DataSource(const sp<DataSource> &source);

    virtual status_t initCheck() const;
    virtual ssize_t readAt(off_t offset, void *data, size_t size);
    virtual status_t getSize(off_t *size);
    virtual uint32_t flags();

    status_t setCachedRange(off_t offset, size_t size);

protected:
    virtual ~MPEG4DataSource();

private:
    Mutex mLock;

    sp<DataSource> mSource;
    off_t mCachedOffset;
    size_t mCachedSize;
    uint8_t *mCache;

    void clearCache();

    MPEG4DataSource(const MPEG4DataSource &);
    MPEG4DataSource &operator=(const MPEG4DataSource &);
};

MPEG4DataSource::MPEG4DataSource(const sp<DataSource> &source)
    : mSource(source),
      mCachedOffset(0),
      mCachedSize(0),
      mCache(NULL) {
}

MPEG4DataSource::~MPEG4DataSource() {
    clearCache();
}

void MPEG4DataSource::clearCache() {
    if (mCache) {
        free(mCache);
        mCache = NULL;
    }

    mCachedOffset = 0;
    mCachedSize = 0;
}

status_t MPEG4DataSource::initCheck() const {
    return mSource->initCheck();
}

ssize_t MPEG4DataSource::readAt(off_t offset, void *data, size_t size) {
    Mutex::Autolock autoLock(mLock);

    if (offset >= mCachedOffset
            && offset + size <= mCachedOffset + mCachedSize) {
        memcpy(data, &mCache[offset - mCachedOffset], size);
        return size;
    }

    return mSource->readAt(offset, data, size);
}

status_t MPEG4DataSource::getSize(off_t *size) {
    return mSource->getSize(size);
}

uint32_t MPEG4DataSource::flags() {
    return mSource->flags();
}

status_t MPEG4DataSource::setCachedRange(off_t offset, size_t size) {
    Mutex::Autolock autoLock(mLock);

    clearCache();

    mCache = (uint8_t *)malloc(size);

    if (mCache == NULL) {
        return -ENOMEM;
    }

    mCachedOffset = offset;
    mCachedSize = size;

    ssize_t err = mSource->readAt(mCachedOffset, mCache, mCachedSize);

    if (err < (ssize_t)size) {
        clearCache();

        return ERROR_IO;
    }

    return OK;
}

////////////////////////////////////////////////////////////////////////////////

static void hexdump(const void *_data, size_t size) {
    const uint8_t *data = (const uint8_t *)_data;
    size_t offset = 0;
    while (offset < size) {
        printf("0x%04x  ", offset);

        size_t n = size - offset;
        if (n > 16) {
            n = 16;
        }

        for (size_t i = 0; i < 16; ++i) {
            if (i == 8) {
                printf(" ");
            }

            if (offset + i < size) {
                printf("%02x ", data[offset + i]);
            } else {
                printf("   ");
            }
        }

        printf(" ");

        for (size_t i = 0; i < n; ++i) {
            if (isprint(data[offset + i])) {
                printf("%c", data[offset + i]);
            } else {
                printf(".");
            }
        }

        printf("\n");

        offset += 16;
    }
}

static const char *FourCC2MIME(uint32_t fourcc) {
    switch (fourcc) {
        case FOURCC('m', 'p', '4', 'a'):
            return MEDIA_MIMETYPE_AUDIO_AAC;

        case FOURCC('s', 'a', 'm', 'r'):
            return MEDIA_MIMETYPE_AUDIO_AMR_NB;

        case FOURCC('s', 'a', 'w', 'b'):
            return MEDIA_MIMETYPE_AUDIO_AMR_WB;

        case FOURCC('m', 'p', '4', 'v'):
            return MEDIA_MIMETYPE_VIDEO_MPEG4;

        case FOURCC('s', '2', '6', '3'):
            return MEDIA_MIMETYPE_VIDEO_H263;

        case FOURCC('a', 'v', 'c', '1'):
            return MEDIA_MIMETYPE_VIDEO_AVC;

        default:
            CHECK(!"should not be here.");
            return NULL;
    }
}

MPEG4Extractor::MPEG4Extractor(const sp<DataSource> &source)
    : mDataSource(source),
      mHaveMetadata(false),
      mHasVideo(false),
      mFirstTrack(NULL),
      mLastTrack(NULL),
      mFileMetaData(new MetaData) {
}

MPEG4Extractor::~MPEG4Extractor() {
    Track *track = mFirstTrack;
    while (track) {
        Track *next = track->next;

        delete track;
        track = next;
    }
    mFirstTrack = mLastTrack = NULL;
}

sp<MetaData> MPEG4Extractor::getMetaData() {
    status_t err;
    if ((err = readMetaData()) != OK) {
        return new MetaData;
    }

    return mFileMetaData;
}

size_t MPEG4Extractor::countTracks() {
    status_t err;
    if ((err = readMetaData()) != OK) {
        return 0;
    }

    size_t n = 0;
    Track *track = mFirstTrack;
    while (track) {
        ++n;
        track = track->next;
    }

    return n;
}

sp<MetaData> MPEG4Extractor::getTrackMetaData(
        size_t index, uint32_t flags) {
    status_t err;
    if ((err = readMetaData()) != OK) {
        return NULL;
    }

    Track *track = mFirstTrack;
    while (index > 0) {
        if (track == NULL) {
            return NULL;
        }

        track = track->next;
        --index;
    }

    if (track == NULL) {
        return NULL;
    }

    if ((flags & kIncludeExtensiveMetaData)
            && !track->includes_expensive_metadata) {
        track->includes_expensive_metadata = true;

        const char *mime;
        CHECK(track->meta->findCString(kKeyMIMEType, &mime));
        if (!strncasecmp("video/", mime, 6)) {
            uint32_t sampleIndex;
            uint32_t sampleTime;
            if (track->sampleTable->findThumbnailSample(&sampleIndex) == OK
                    && track->sampleTable->getMetaDataForSample(
                        sampleIndex, NULL /* offset */, NULL /* size */,
                        &sampleTime) == OK) {
                track->meta->setInt64(
                        kKeyThumbnailTime,
                        ((int64_t)sampleTime * 1000000) / track->timescale);
            }
        }
    }

    return track->meta;
}

status_t MPEG4Extractor::readMetaData() {
    if (mHaveMetadata) {
        return OK;
    }

    off_t offset = 0;
    status_t err;
    while ((err = parseChunk(&offset, 0)) == OK) {
    }

    if (mHaveMetadata) {
        if (mHasVideo) {
            mFileMetaData->setCString(kKeyMIMEType, "video/mp4");
        } else {
            mFileMetaData->setCString(kKeyMIMEType, "audio/mp4");
        }

        return OK;
    }

    return err;
}

static void MakeFourCCString(uint32_t x, char *s) {
    s[0] = x >> 24;
    s[1] = (x >> 16) & 0xff;
    s[2] = (x >> 8) & 0xff;
    s[3] = x & 0xff;
    s[4] = '\0';
}

struct PathAdder {
    PathAdder(Vector<uint32_t> *path, uint32_t chunkType)
        : mPath(path) {
        mPath->push(chunkType);
    }

    ~PathAdder() {
        mPath->pop();
    }

private:
    Vector<uint32_t> *mPath;

    PathAdder(const PathAdder &);
    PathAdder &operator=(const PathAdder &);
};

static bool underMetaDataPath(const Vector<uint32_t> &path) {
    return path.size() >= 5
        && path[0] == FOURCC('m', 'o', 'o', 'v')
        && path[1] == FOURCC('u', 'd', 't', 'a')
        && path[2] == FOURCC('m', 'e', 't', 'a')
        && path[3] == FOURCC('i', 'l', 's', 't');
}

// Given a time in seconds since Jan 1 1904, produce a human-readable string.
static void convertTimeToDate(int64_t time_1904, String8 *s) {
    time_t time_1970 = time_1904 - (((66 * 365 + 17) * 24) * 3600);

    char tmp[32];
    strftime(tmp, sizeof(tmp), "%Y%m%dT%H%M%S.000Z", gmtime(&time_1970));

    s->setTo(tmp);
}

status_t MPEG4Extractor::parseChunk(off_t *offset, int depth) {
    uint32_t hdr[2];
    if (mDataSource->readAt(*offset, hdr, 8) < 8) {
        return ERROR_IO;
    }
    uint64_t chunk_size = ntohl(hdr[0]);
    uint32_t chunk_type = ntohl(hdr[1]);
    off_t data_offset = *offset + 8;

    if (chunk_size == 1) {
        if (mDataSource->readAt(*offset + 8, &chunk_size, 8) < 8) {
            return ERROR_IO;
        }
        chunk_size = ntoh64(chunk_size);
        data_offset += 8;

        if (chunk_size < 16) {
            // The smallest valid chunk is 16 bytes long in this case.
            return ERROR_MALFORMED;
        }
    } else if (chunk_size < 8) {
        // The smallest valid chunk is 8 bytes long.
        return ERROR_MALFORMED;
    }

    char chunk[5];
    MakeFourCCString(chunk_type, chunk);

#if 0
    static const char kWhitespace[] = "                                        ";
    const char *indent = &kWhitespace[sizeof(kWhitespace) - 1 - 2 * depth];
    printf("%sfound chunk '%s' of size %lld\n", indent, chunk, chunk_size);

    char buffer[256];
    size_t n = chunk_size;
    if (n > sizeof(buffer)) {
        n = sizeof(buffer);
    }
    if (mDataSource->readAt(*offset, buffer, n)
            < (ssize_t)n) {
        return ERROR_IO;
    }

    hexdump(buffer, n);
#endif

    PathAdder autoAdder(&mPath, chunk_type);

    off_t chunk_data_size = *offset + chunk_size - data_offset;

    if (chunk_type != FOURCC('c', 'p', 'r', 't')
            && mPath.size() == 5 && underMetaDataPath(mPath)) {
        off_t stop_offset = *offset + chunk_size;
        *offset = data_offset;
        while (*offset < stop_offset) {
            status_t err = parseChunk(offset, depth + 1);
            if (err != OK) {
                return err;
            }
        }

        if (*offset != stop_offset) {
            return ERROR_MALFORMED;
        }

        return OK;
    }

    switch(chunk_type) {
        case FOURCC('m', 'o', 'o', 'v'):
        case FOURCC('t', 'r', 'a', 'k'):
        case FOURCC('m', 'd', 'i', 'a'):
        case FOURCC('m', 'i', 'n', 'f'):
        case FOURCC('d', 'i', 'n', 'f'):
        case FOURCC('s', 't', 'b', 'l'):
        case FOURCC('m', 'v', 'e', 'x'):
        case FOURCC('m', 'o', 'o', 'f'):
        case FOURCC('t', 'r', 'a', 'f'):
        case FOURCC('m', 'f', 'r', 'a'):
        case FOURCC('u', 'd', 't', 'a'):
        case FOURCC('i', 'l', 's', 't'):
        {
            if (chunk_type == FOURCC('s', 't', 'b', 'l')) {
                LOGV("sampleTable chunk is %d bytes long.", (size_t)chunk_size);

                if (mDataSource->flags()
                        & (DataSource::kWantsPrefetching
                            | DataSource::kIsCachingDataSource)) {
                    sp<MPEG4DataSource> cachedSource =
                        new MPEG4DataSource(mDataSource);

                    if (cachedSource->setCachedRange(*offset, chunk_size) == OK) {
                        mDataSource = cachedSource;
                    }
                }

                mLastTrack->sampleTable = new SampleTable(mDataSource);
            }

            bool isTrack = false;
            if (chunk_type == FOURCC('t', 'r', 'a', 'k')) {
                isTrack = true;

                Track *track = new Track;
                track->next = NULL;
                if (mLastTrack) {
                    mLastTrack->next = track;
                } else {
                    mFirstTrack = track;
                }
                mLastTrack = track;

                track->meta = new MetaData;
                track->includes_expensive_metadata = false;
                track->skipTrack = false;
                track->timescale = 0;
                track->meta->setCString(kKeyMIMEType, "application/octet-stream");
            }

            off_t stop_offset = *offset + chunk_size;
            *offset = data_offset;
            while (*offset < stop_offset) {
                status_t err = parseChunk(offset, depth + 1);
                if (err != OK) {
                    return err;
                }
            }

            if (*offset != stop_offset) {
                return ERROR_MALFORMED;
            }

            if (isTrack) {
                if (mLastTrack->skipTrack) {
                    Track *cur = mFirstTrack;

                    if (cur == mLastTrack) {
                        delete cur;
                        mFirstTrack = mLastTrack = NULL;
                    } else {
                        while (cur && cur->next != mLastTrack) {
                            cur = cur->next;
                        }
                        cur->next = NULL;
                        delete mLastTrack;
                        mLastTrack = cur;
                    }

                    return OK;
                }

                status_t err = verifyTrack(mLastTrack);

                if (err != OK) {
                    return err;
                }
            } else if (chunk_type == FOURCC('m', 'o', 'o', 'v')) {
                mHaveMetadata = true;

                return UNKNOWN_ERROR;  // Return a dummy error.
            }
            break;
        }

        case FOURCC('t', 'k', 'h', 'd'):
        {
            status_t err;
            if ((err = parseTrackHeader(data_offset, chunk_data_size)) != OK) {
                return err;
            }

            *offset += chunk_size;
            break;
        }

        case FOURCC('m', 'd', 'h', 'd'):
        {
            if (chunk_data_size < 4) {
                return ERROR_MALFORMED;
            }

            uint8_t version;
            if (mDataSource->readAt(
                        data_offset, &version, sizeof(version))
                    < (ssize_t)sizeof(version)) {
                return ERROR_IO;
            }

            off_t timescale_offset;

            if (version == 1) {
                timescale_offset = data_offset + 4 + 16;
            } else if (version == 0) {
                timescale_offset = data_offset + 4 + 8;
            } else {
                return ERROR_IO;
            }

            uint32_t timescale;
            if (mDataSource->readAt(
                        timescale_offset, &timescale, sizeof(timescale))
                    < (ssize_t)sizeof(timescale)) {
                return ERROR_IO;
            }

            mLastTrack->timescale = ntohl(timescale);

            int64_t duration;
            if (version == 1) {
                if (mDataSource->readAt(
                            timescale_offset + 4, &duration, sizeof(duration))
                        < (ssize_t)sizeof(duration)) {
                    return ERROR_IO;
                }
                duration = ntoh64(duration);
            } else {
                int32_t duration32;
                if (mDataSource->readAt(
                            timescale_offset + 4, &duration32, sizeof(duration32))
                        < (ssize_t)sizeof(duration32)) {
                    return ERROR_IO;
                }
                duration = ntohl(duration32);
            }
            mLastTrack->meta->setInt64(
                    kKeyDuration, (duration * 1000000) / mLastTrack->timescale);

            *offset += chunk_size;
            break;
        }

        case FOURCC('s', 't', 's', 'd'):
        {
            if (chunk_data_size < 8) {
                return ERROR_MALFORMED;
            }

            uint8_t buffer[8];
            if (chunk_data_size < (off_t)sizeof(buffer)) {
                return ERROR_MALFORMED;
            }

            if (mDataSource->readAt(
                        data_offset, buffer, 8) < 8) {
                return ERROR_IO;
            }

            if (U32_AT(buffer) != 0) {
                // Should be version 0, flags 0.
                return ERROR_MALFORMED;
            }

            uint32_t entry_count = U32_AT(&buffer[4]);

            if (entry_count > 1) {
                // For now we only support a single type of media per track.

                mLastTrack->skipTrack = true;
                *offset += chunk_size;
                break;
            }

            off_t stop_offset = *offset + chunk_size;
            *offset = data_offset + 8;
            for (uint32_t i = 0; i < entry_count; ++i) {
                status_t err = parseChunk(offset, depth + 1);
                if (err != OK) {
                    return err;
                }
            }

            if (*offset != stop_offset) {
                return ERROR_MALFORMED;
            }
            break;
        }

        case FOURCC('m', 'p', '4', 'a'):
        case FOURCC('s', 'a', 'm', 'r'):
        case FOURCC('s', 'a', 'w', 'b'):
        {
            uint8_t buffer[8 + 20];
            if (chunk_data_size < (ssize_t)sizeof(buffer)) {
                // Basic AudioSampleEntry size.
                return ERROR_MALFORMED;
            }

            if (mDataSource->readAt(
                        data_offset, buffer, sizeof(buffer)) < (ssize_t)sizeof(buffer)) {
                return ERROR_IO;
            }

            uint16_t data_ref_index = U16_AT(&buffer[6]);
            uint16_t num_channels = U16_AT(&buffer[16]);

            uint16_t sample_size = U16_AT(&buffer[18]);
            uint32_t sample_rate = U32_AT(&buffer[24]) >> 16;

            if (!strcasecmp(MEDIA_MIMETYPE_AUDIO_AMR_NB,
                            FourCC2MIME(chunk_type))) {
                // AMR NB audio is always mono, 8kHz
                num_channels = 1;
                sample_rate = 8000;
            } else if (!strcasecmp(MEDIA_MIMETYPE_AUDIO_AMR_WB,
                               FourCC2MIME(chunk_type))) {
                // AMR WB audio is always mono, 16kHz
                num_channels = 1;
                sample_rate = 16000;
            }

#if 0
            printf("*** coding='%s' %d channels, size %d, rate %d\n",
                   chunk, num_channels, sample_size, sample_rate);
#endif

            mLastTrack->meta->setCString(kKeyMIMEType, FourCC2MIME(chunk_type));
            mLastTrack->meta->setInt32(kKeyChannelCount, num_channels);
            mLastTrack->meta->setInt32(kKeySampleRate, sample_rate);

            off_t stop_offset = *offset + chunk_size;
            *offset = data_offset + sizeof(buffer);
            while (*offset < stop_offset) {
                status_t err = parseChunk(offset, depth + 1);
                if (err != OK) {
                    return err;
                }
            }

            if (*offset != stop_offset) {
                return ERROR_MALFORMED;
            }
            break;
        }

        case FOURCC('m', 'p', '4', 'v'):
        case FOURCC('s', '2', '6', '3'):
        case FOURCC('a', 'v', 'c', '1'):
        {
            mHasVideo = true;

            uint8_t buffer[78];
            if (chunk_data_size < (ssize_t)sizeof(buffer)) {
                // Basic VideoSampleEntry size.
                return ERROR_MALFORMED;
            }

            if (mDataSource->readAt(
                        data_offset, buffer, sizeof(buffer)) < (ssize_t)sizeof(buffer)) {
                return ERROR_IO;
            }

            uint16_t data_ref_index = U16_AT(&buffer[6]);
            uint16_t width = U16_AT(&buffer[6 + 18]);
            uint16_t height = U16_AT(&buffer[6 + 20]);

            // printf("*** coding='%s' width=%d height=%d\n",
            //        chunk, width, height);

            mLastTrack->meta->setCString(kKeyMIMEType, FourCC2MIME(chunk_type));
            mLastTrack->meta->setInt32(kKeyWidth, width);
            mLastTrack->meta->setInt32(kKeyHeight, height);

            off_t stop_offset = *offset + chunk_size;
            *offset = data_offset + sizeof(buffer);
            while (*offset < stop_offset) {
                status_t err = parseChunk(offset, depth + 1);
                if (err != OK) {
                    return err;
                }
            }

            if (*offset != stop_offset) {
                return ERROR_MALFORMED;
            }
            break;
        }

        case FOURCC('s', 't', 'c', 'o'):
        case FOURCC('c', 'o', '6', '4'):
        {
            status_t err =
                mLastTrack->sampleTable->setChunkOffsetParams(
                        chunk_type, data_offset, chunk_data_size);

            if (err != OK) {
                return err;
            }

            *offset += chunk_size;
            break;
        }

        case FOURCC('s', 't', 's', 'c'):
        {
            status_t err =
                mLastTrack->sampleTable->setSampleToChunkParams(
                        data_offset, chunk_data_size);

            if (err != OK) {
                return err;
            }

            *offset += chunk_size;
            break;
        }

        case FOURCC('s', 't', 's', 'z'):
        case FOURCC('s', 't', 'z', '2'):
        {
            status_t err =
                mLastTrack->sampleTable->setSampleSizeParams(
                        chunk_type, data_offset, chunk_data_size);

            if (err != OK) {
                return err;
            }

            size_t max_size;
            err = mLastTrack->sampleTable->getMaxSampleSize(&max_size);

            if (err != OK) {
                return err;
            }

            // Assume that a given buffer only contains at most 10 fragments,
            // each fragment originally prefixed with a 2 byte length will
            // have a 4 byte header (0x00 0x00 0x00 0x01) after conversion,
            // and thus will grow by 2 bytes per fragment.
            mLastTrack->meta->setInt32(kKeyMaxInputSize, max_size + 10 * 2);

            *offset += chunk_size;
            break;
        }

        case FOURCC('s', 't', 't', 's'):
        {
            status_t err =
                mLastTrack->sampleTable->setTimeToSampleParams(
                        data_offset, chunk_data_size);

            if (err != OK) {
                return err;
            }

            *offset += chunk_size;
            break;
        }

        case FOURCC('s', 't', 's', 's'):
        {
            status_t err =
                mLastTrack->sampleTable->setSyncSampleParams(
                        data_offset, chunk_data_size);

            if (err != OK) {
                return err;
            }

            *offset += chunk_size;
            break;
        }

        case FOURCC('e', 's', 'd', 's'):
        {
            if (chunk_data_size < 4) {
                return ERROR_MALFORMED;
            }

            uint8_t buffer[256];
            if (chunk_data_size > (off_t)sizeof(buffer)) {
                return ERROR_BUFFER_TOO_SMALL;
            }

            if (mDataSource->readAt(
                        data_offset, buffer, chunk_data_size) < chunk_data_size) {
                return ERROR_IO;
            }

            if (U32_AT(buffer) != 0) {
                // Should be version 0, flags 0.
                return ERROR_MALFORMED;
            }

            mLastTrack->meta->setData(
                    kKeyESDS, kTypeESDS, &buffer[4], chunk_data_size - 4);

            if (mPath.size() >= 2
                    && mPath[mPath.size() - 2] == FOURCC('m', 'p', '4', 'a')) {
                // Information from the ESDS must be relied on for proper
                // setup of sample rate and channel count for MPEG4 Audio.
                // The generic header appears to only contain generic
                // information...

                status_t err = updateAudioTrackInfoFromESDS_MPEG4Audio(
                        &buffer[4], chunk_data_size - 4);

                if (err != OK) {
                    return err;
                }
            }

            *offset += chunk_size;
            break;
        }

        case FOURCC('a', 'v', 'c', 'C'):
        {
            char buffer[256];
            if (chunk_data_size > (off_t)sizeof(buffer)) {
                return ERROR_BUFFER_TOO_SMALL;
            }

            if (mDataSource->readAt(
                        data_offset, buffer, chunk_data_size) < chunk_data_size) {
                return ERROR_IO;
            }

            mLastTrack->meta->setData(
                    kKeyAVCC, kTypeAVCC, buffer, chunk_data_size);

            *offset += chunk_size;
            break;
        }

        case FOURCC('m', 'e', 't', 'a'):
        {
            uint8_t buffer[4];
            if (chunk_data_size < (off_t)sizeof(buffer)) {
                return ERROR_MALFORMED;
            }

            if (mDataSource->readAt(
                        data_offset, buffer, 4) < 4) {
                return ERROR_IO;
            }

            if (U32_AT(buffer) != 0) {
                // Should be version 0, flags 0.

                // If it's not, let's assume this is one of those
                // apparently malformed chunks that don't have flags
                // and completely different semantics than what's
                // in the MPEG4 specs and skip it.
                *offset += chunk_size;
                return OK;
            }

            off_t stop_offset = *offset + chunk_size;
            *offset = data_offset + sizeof(buffer);
            while (*offset < stop_offset) {
                status_t err = parseChunk(offset, depth + 1);
                if (err != OK) {
                    return err;
                }
            }

            if (*offset != stop_offset) {
                return ERROR_MALFORMED;
            }
            break;
        }

        case FOURCC('d', 'a', 't', 'a'):
        {
            if (mPath.size() == 6 && underMetaDataPath(mPath)) {
                status_t err = parseMetaData(data_offset, chunk_data_size);

                if (err != OK) {
                    return err;
                }
            }

            *offset += chunk_size;
            break;
        }

        case FOURCC('m', 'v', 'h', 'd'):
        {
            if (chunk_data_size < 12) {
                return ERROR_MALFORMED;
            }

            uint8_t header[12];
            if (mDataSource->readAt(
                        data_offset, header, sizeof(header))
                    < (ssize_t)sizeof(header)) {
                return ERROR_IO;
            }

            int64_t creationTime;
            if (header[0] == 1) {
                creationTime = U64_AT(&header[4]);
            } else if (header[0] != 0) {
                return ERROR_MALFORMED;
            } else {
                creationTime = U32_AT(&header[4]);
            }

            String8 s;
            convertTimeToDate(creationTime, &s);

            mFileMetaData->setCString(kKeyDate, s.string());

            *offset += chunk_size;
            break;
        }

        default:
        {
            *offset += chunk_size;
            break;
        }
    }

    return OK;
}

status_t MPEG4Extractor::parseTrackHeader(
        off_t data_offset, off_t data_size) {
    if (data_size < 4) {
        return ERROR_MALFORMED;
    }

    uint8_t version;
    if (mDataSource->readAt(data_offset, &version, 1) < 1) {
        return ERROR_IO;
    }

    size_t dynSize = (version == 1) ? 36 : 24;

    uint8_t buffer[36 + 60];

    if (data_size != (off_t)dynSize + 60) {
        return ERROR_MALFORMED;
    }

    if (mDataSource->readAt(
                data_offset, buffer, data_size) < (ssize_t)data_size) {
        return ERROR_IO;
    }

    uint64_t ctime, mtime, duration;
    int32_t id;

    if (version == 1) {
        ctime = U64_AT(&buffer[4]);
        mtime = U64_AT(&buffer[12]);
        id = U32_AT(&buffer[20]);
        duration = U64_AT(&buffer[28]);
    } else if (version == 0) {
        ctime = U32_AT(&buffer[4]);
        mtime = U32_AT(&buffer[8]);
        id = U32_AT(&buffer[12]);
        duration = U32_AT(&buffer[20]);
    }

    size_t matrixOffset = dynSize + 16;
    int32_t a00 = U32_AT(&buffer[matrixOffset]);
    int32_t a01 = U32_AT(&buffer[matrixOffset + 4]);
    int32_t dx = U32_AT(&buffer[matrixOffset + 8]);
    int32_t a10 = U32_AT(&buffer[matrixOffset + 12]);
    int32_t a11 = U32_AT(&buffer[matrixOffset + 16]);
    int32_t dy = U32_AT(&buffer[matrixOffset + 20]);

#if 0
    LOGI("x' = %.2f * x + %.2f * y + %.2f",
         a00 / 65536.0f, a01 / 65536.0f, dx / 65536.0f);
    LOGI("y' = %.2f * x + %.2f * y + %.2f",
         a10 / 65536.0f, a11 / 65536.0f, dy / 65536.0f);
#endif

    uint32_t rotationDegrees;

    static const int32_t kFixedOne = 0x10000;
    if (a00 == kFixedOne && a01 == 0 && a10 == 0 && a11 == kFixedOne) {
        // Identity, no rotation
        rotationDegrees = 0;
    } else if (a00 == 0 && a01 == kFixedOne && a10 == -kFixedOne && a11 == 0) {
        rotationDegrees = 90;
    } else if (a00 == 0 && a01 == -kFixedOne && a10 == kFixedOne && a11 == 0) {
        rotationDegrees = 270;
    } else if (a00 == -kFixedOne && a01 == 0 && a10 == 0 && a11 == -kFixedOne) {
        rotationDegrees = 180;
    } else {
        LOGW("We only support 0,90,180,270 degree rotation matrices");
        rotationDegrees = 0;
    }

    if (rotationDegrees != 0) {
        mLastTrack->meta->setInt32(kKeyRotation, rotationDegrees);
    }

#if 0
    uint32_t width = U32_AT(&buffer[dynSize + 52]);
    uint32_t height = U32_AT(&buffer[dynSize + 56]);
#endif

    return OK;
}

status_t MPEG4Extractor::parseMetaData(off_t offset, size_t size) {
    if (size < 4) {
        return ERROR_MALFORMED;
    }

    uint8_t *buffer = new uint8_t[size + 1];
    if (mDataSource->readAt(
                offset, buffer, size) != (ssize_t)size) {
        delete[] buffer;
        buffer = NULL;

        return ERROR_IO;
    }

    uint32_t flags = U32_AT(buffer);

    uint32_t metadataKey = 0;
    switch (mPath[4]) {
        case FOURCC(0xa9, 'a', 'l', 'b'):
        {
            metadataKey = kKeyAlbum;
            break;
        }
        case FOURCC(0xa9, 'A', 'R', 'T'):
        {
            metadataKey = kKeyArtist;
            break;
        }
        case FOURCC('a', 'A', 'R', 'T'):
        {
            metadataKey = kKeyAlbumArtist;
            break;
        }
        case FOURCC(0xa9, 'd', 'a', 'y'):
        {
            metadataKey = kKeyYear;
            break;
        }
        case FOURCC(0xa9, 'n', 'a', 'm'):
        {
            metadataKey = kKeyTitle;
            break;
        }
        case FOURCC(0xa9, 'w', 'r', 't'):
        {
            metadataKey = kKeyWriter;
            break;
        }
        case FOURCC('c', 'o', 'v', 'r'):
        {
            metadataKey = kKeyAlbumArt;
            break;
        }
        case FOURCC('g', 'n', 'r', 'e'):
        {
            metadataKey = kKeyGenre;
            break;
        }
        case FOURCC(0xa9, 'g', 'e', 'n'):
        {
            metadataKey = kKeyGenre;
            break;
        }
        case FOURCC('c', 'p', 'i', 'l'):
        {
            if (size == 9 && flags == 21) {
                char tmp[16];
                sprintf(tmp, "%d",
                        (int)buffer[size - 1]);

                mFileMetaData->setCString(kKeyCompilation, tmp);
            }
            break;
        }
        case FOURCC('t', 'r', 'k', 'n'):
        {
            if (size == 16 && flags == 0) {
                char tmp[16];
                sprintf(tmp, "%d/%d",
                        (int)buffer[size - 5], (int)buffer[size - 3]);

                mFileMetaData->setCString(kKeyCDTrackNumber, tmp);
            }
            break;
        }
        case FOURCC('d', 'i', 's', 'k'):
        {
            if (size == 14 && flags == 0) {
                char tmp[16];
                sprintf(tmp, "%d/%d",
                        (int)buffer[size - 3], (int)buffer[size - 1]);

                mFileMetaData->setCString(kKeyDiscNumber, tmp);
            }
            break;
        }

        default:
            break;
    }

    if (size >= 8 && metadataKey) {
        if (metadataKey == kKeyAlbumArt) {
            mFileMetaData->setData(
                    kKeyAlbumArt, MetaData::TYPE_NONE,
                    buffer + 8, size - 8);
        } else if (metadataKey == kKeyGenre) {
            if (flags == 0) {
                // uint8_t genre code, iTunes genre codes are
                // the standard id3 codes, except they start
                // at 1 instead of 0 (e.g. Pop is 14, not 13)
                // We use standard id3 numbering, so subtract 1.
                int genrecode = (int)buffer[size - 1];
                genrecode--;
                if (genrecode < 0) {
                    genrecode = 255; // reserved for 'unknown genre'
                }
                char genre[10];
                sprintf(genre, "%d", genrecode);

                mFileMetaData->setCString(metadataKey, genre);
            } else if (flags == 1) {
                // custom genre string
                buffer[size] = '\0';

                mFileMetaData->setCString(
                        metadataKey, (const char *)buffer + 8);
            }
        } else {
            buffer[size] = '\0';

            mFileMetaData->setCString(
                    metadataKey, (const char *)buffer + 8);
        }
    }

    delete[] buffer;
    buffer = NULL;

    return OK;
}

sp<MediaSource> MPEG4Extractor::getTrack(size_t index) {
    status_t err;
    if ((err = readMetaData()) != OK) {
        return NULL;
    }

    Track *track = mFirstTrack;
    while (index > 0) {
        if (track == NULL) {
            return NULL;
        }

        track = track->next;
        --index;
    }

    if (track == NULL) {
        return NULL;
    }

    return new MPEG4Source(
            track->meta, mDataSource, track->timescale, track->sampleTable);
}

// static
status_t MPEG4Extractor::verifyTrack(Track *track) {
    const char *mime;
    CHECK(track->meta->findCString(kKeyMIMEType, &mime));

    uint32_t type;
    const void *data;
    size_t size;
    if (!strcasecmp(mime, MEDIA_MIMETYPE_VIDEO_AVC)) {
        if (!track->meta->findData(kKeyAVCC, &type, &data, &size)
                || type != kTypeAVCC) {
            return ERROR_MALFORMED;
        }
    } else if (!strcasecmp(mime, MEDIA_MIMETYPE_VIDEO_MPEG4)
            || !strcasecmp(mime, MEDIA_MIMETYPE_AUDIO_AAC)) {
        if (!track->meta->findData(kKeyESDS, &type, &data, &size)
                || type != kTypeESDS) {
            return ERROR_MALFORMED;
        }
    }

    return OK;
}

status_t MPEG4Extractor::updateAudioTrackInfoFromESDS_MPEG4Audio(
        const void *esds_data, size_t esds_size) {
    ESDS esds(esds_data, esds_size);

    uint8_t objectTypeIndication;
    if (esds.getObjectTypeIndication(&objectTypeIndication) != OK) {
        return ERROR_MALFORMED;
    }

    if (objectTypeIndication == 0xe1) {
        // This isn't MPEG4 audio at all, it's QCELP 14k...
        mLastTrack->meta->setCString(kKeyMIMEType, MEDIA_MIMETYPE_AUDIO_QCELP);
        return OK;
    }

    const uint8_t *csd;
    size_t csd_size;
    if (esds.getCodecSpecificInfo(
                (const void **)&csd, &csd_size) != OK) {
        return ERROR_MALFORMED;
    }

#if 0
    printf("ESD of size %d\n", csd_size);
    hexdump(csd, csd_size);
#endif

    if (csd_size == 0) {
        // There's no further information, i.e. no codec specific data
        // Let's assume that the information provided in the mpeg4 headers
        // is accurate and hope for the best.

        return OK;
    }

    if (csd_size < 2) {
        return ERROR_MALFORMED;
    }

    uint32_t objectType = csd[0] >> 3;

    if (objectType == 31) {
        return ERROR_UNSUPPORTED;
    }

    uint32_t freqIndex = (csd[0] & 7) << 1 | (csd[1] >> 7);
    int32_t sampleRate = 0;
    int32_t numChannels = 0;
    if (freqIndex == 15) {
        if (csd_size < 5) {
            return ERROR_MALFORMED;
        }

        sampleRate = (csd[1] & 0x7f) << 17
                        | csd[2] << 9
                        | csd[3] << 1
                        | (csd[4] >> 7);

        numChannels = (csd[4] >> 3) & 15;
    } else {
        static uint32_t kSamplingRate[] = {
            96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050,
            16000, 12000, 11025, 8000, 7350
        };

        if (freqIndex == 13 || freqIndex == 14) {
            return ERROR_MALFORMED;
        }

        sampleRate = kSamplingRate[freqIndex];
        numChannels = (csd[1] >> 3) & 15;
    }

    if (numChannels == 0) {
        return ERROR_UNSUPPORTED;
    }

    int32_t prevSampleRate;
    CHECK(mLastTrack->meta->findInt32(kKeySampleRate, &prevSampleRate));

    if (prevSampleRate != sampleRate) {
        LOGV("mpeg4 audio sample rate different from previous setting. "
             "was: %d, now: %d", prevSampleRate, sampleRate);
    }

    mLastTrack->meta->setInt32(kKeySampleRate, sampleRate);

    int32_t prevChannelCount;
    CHECK(mLastTrack->meta->findInt32(kKeyChannelCount, &prevChannelCount));

    if (prevChannelCount != numChannels) {
        LOGV("mpeg4 audio channel count different from previous setting. "
             "was: %d, now: %d", prevChannelCount, numChannels);
    }

    mLastTrack->meta->setInt32(kKeyChannelCount, numChannels);

    return OK;
}

////////////////////////////////////////////////////////////////////////////////

MPEG4Source::MPEG4Source(
        const sp<MetaData> &format,
        const sp<DataSource> &dataSource,
        int32_t timeScale,
        const sp<SampleTable> &sampleTable)
    : mFormat(format),
      mDataSource(dataSource),
      mTimescale(timeScale),
      mSampleTable(sampleTable),
      mCurrentSampleIndex(0),
      mIsAVC(false),
      mNALLengthSize(0),
      mStarted(false),
      mGroup(NULL),
      mBuffer(NULL),
      mWantsNALFragments(false),
      mSrcBuffer(NULL) {
    const char *mime;
    bool success = mFormat->findCString(kKeyMIMEType, &mime);
    CHECK(success);

    mIsAVC = !strcasecmp(mime, MEDIA_MIMETYPE_VIDEO_AVC);

    if (mIsAVC) {
        uint32_t type;
        const void *data;
        size_t size;
        CHECK(format->findData(kKeyAVCC, &type, &data, &size));

        const uint8_t *ptr = (const uint8_t *)data;

        CHECK(size >= 7);
        CHECK_EQ((unsigned)ptr[0], 1u);  // configurationVersion == 1

        // The number of bytes used to encode the length of a NAL unit.
        mNALLengthSize = 1 + (ptr[4] & 3);
    }
}

MPEG4Source::~MPEG4Source() {
    if (mStarted) {
        stop();
    }
}

status_t MPEG4Source::start(MetaData *params) {
    Mutex::Autolock autoLock(mLock);

    CHECK(!mStarted);

    int32_t val;
    if (params && params->findInt32(kKeyWantsNALFragments, &val)
        && val != 0) {
        mWantsNALFragments = true;
    } else {
        mWantsNALFragments = false;
    }

    mGroup = new MediaBufferGroup;

    int32_t max_size;
    CHECK(mFormat->findInt32(kKeyMaxInputSize, &max_size));

    mGroup->add_buffer(new MediaBuffer(max_size));

    mSrcBuffer = new uint8_t[max_size];

    mStarted = true;

    return OK;
}

status_t MPEG4Source::stop() {
    Mutex::Autolock autoLock(mLock);

    CHECK(mStarted);

    if (mBuffer != NULL) {
        mBuffer->release();
        mBuffer = NULL;
    }

    delete[] mSrcBuffer;
    mSrcBuffer = NULL;

    delete mGroup;
    mGroup = NULL;

    mStarted = false;
    mCurrentSampleIndex = 0;

    return OK;
}

sp<MetaData> MPEG4Source::getFormat() {
    Mutex::Autolock autoLock(mLock);

    return mFormat;
}

size_t MPEG4Source::parseNALSize(const uint8_t *data) const {
    switch (mNALLengthSize) {
        case 1:
            return *data;
        case 2:
            return U16_AT(data);
        case 3:
            return ((size_t)data[0] << 16) | U16_AT(&data[1]);
        case 4:
            return U32_AT(data);
    }

    // This cannot happen, mNALLengthSize springs to life by adding 1 to
    // a 2-bit integer.
    CHECK(!"Should not be here.");

    return 0;
}

status_t MPEG4Source::read(
        MediaBuffer **out, const ReadOptions *options) {
    Mutex::Autolock autoLock(mLock);

    CHECK(mStarted);

    *out = NULL;

    int64_t targetSampleTimeUs = -1;

    int64_t seekTimeUs;
    ReadOptions::SeekMode mode;
    if (options && options->getSeekTo(&seekTimeUs, &mode)) {
        uint32_t findFlags = 0;
        switch (mode) {
            case ReadOptions::SEEK_PREVIOUS_SYNC:
                findFlags = SampleTable::kFlagBefore;
                break;
            case ReadOptions::SEEK_NEXT_SYNC:
                findFlags = SampleTable::kFlagAfter;
                break;
            case ReadOptions::SEEK_CLOSEST_SYNC:
            case ReadOptions::SEEK_CLOSEST:
                findFlags = SampleTable::kFlagClosest;
                break;
            default:
                CHECK(!"Should not be here.");
                break;
        }

        uint32_t sampleIndex;
        status_t err = mSampleTable->findSampleAtTime(
                seekTimeUs * mTimescale / 1000000,
                &sampleIndex, findFlags);

        if (mode == ReadOptions::SEEK_CLOSEST) {
            // We found the closest sample already, now we want the sync
            // sample preceding it (or the sample itself of course), even
            // if the subsequent sync sample is closer.
            findFlags = SampleTable::kFlagBefore;
        }

        uint32_t syncSampleIndex;
        if (err == OK) {
            err = mSampleTable->findSyncSampleNear(
                    sampleIndex, &syncSampleIndex, findFlags);
        }

        if (err != OK) {
            if (err == ERROR_OUT_OF_RANGE) {
                // An attempt to seek past the end of the stream would
                // normally cause this ERROR_OUT_OF_RANGE error. Propagating
                // this all the way to the MediaPlayer would cause abnormal
                // termination. Legacy behaviour appears to be to behave as if
                // we had seeked to the end of stream, ending normally.
                err = ERROR_END_OF_STREAM;
            }
            return err;
        }

        uint32_t sampleTime;
        CHECK_EQ((status_t)OK, mSampleTable->getMetaDataForSample(
                    sampleIndex, NULL, NULL, &sampleTime));

        if (mode == ReadOptions::SEEK_CLOSEST) {
            targetSampleTimeUs = (sampleTime * 1000000ll) / mTimescale;
        }

#if 0
        uint32_t syncSampleTime;
        CHECK_EQ(OK, mSampleTable->getMetaDataForSample(
                    syncSampleIndex, NULL, NULL, &syncSampleTime));

        LOGI("seek to time %lld us => sample at time %lld us, "
             "sync sample at time %lld us",
             seekTimeUs,
             sampleTime * 1000000ll / mTimescale,
             syncSampleTime * 1000000ll / mTimescale);
#endif

        mCurrentSampleIndex = syncSampleIndex;
        if (mBuffer != NULL) {
            mBuffer->release();
            mBuffer = NULL;
        }

        // fall through
    }

    off_t offset;
    size_t size;
    uint32_t dts;
    bool isSyncSample;
    bool newBuffer = false;
    if (mBuffer == NULL) {
        newBuffer = true;

        status_t err =
            mSampleTable->getMetaDataForSample(
                    mCurrentSampleIndex, &offset, &size, &dts, &isSyncSample);

        if (err != OK) {
            return err;
        }

        err = mGroup->acquire_buffer(&mBuffer);

        if (err != OK) {
            CHECK(mBuffer == NULL);
            return err;
        }
    }

    if (!mIsAVC || mWantsNALFragments) {
        if (newBuffer) {
            ssize_t num_bytes_read =
                mDataSource->readAt(offset, (uint8_t *)mBuffer->data(), size);

            if (num_bytes_read < (ssize_t)size) {
                mBuffer->release();
                mBuffer = NULL;

                return ERROR_IO;
            }

            CHECK(mBuffer != NULL);
            mBuffer->set_range(0, size);
            mBuffer->meta_data()->clear();
            mBuffer->meta_data()->setInt64(
                    kKeyTime, ((int64_t)dts * 1000000) / mTimescale);

            if (targetSampleTimeUs >= 0) {
                mBuffer->meta_data()->setInt64(
                        kKeyTargetTime, targetSampleTimeUs);
            }

            if (isSyncSample) {
                mBuffer->meta_data()->setInt32(kKeyIsSyncFrame, 1);
            }

            ++mCurrentSampleIndex;
        }

        if (!mIsAVC) {
            *out = mBuffer;
            mBuffer = NULL;

            return OK;
        }

        // Each NAL unit is split up into its constituent fragments and
        // each one of them returned in its own buffer.

        CHECK(mBuffer->range_length() >= mNALLengthSize);

        const uint8_t *src =
            (const uint8_t *)mBuffer->data() + mBuffer->range_offset();

        size_t nal_size = parseNALSize(src);
        if (mBuffer->range_length() < mNALLengthSize + nal_size) {
            LOGE("incomplete NAL unit.");

            mBuffer->release();
            mBuffer = NULL;

            return ERROR_MALFORMED;
        }

        MediaBuffer *clone = mBuffer->clone();
        CHECK(clone != NULL);
        clone->set_range(mBuffer->range_offset() + mNALLengthSize, nal_size);

        CHECK(mBuffer != NULL);
        mBuffer->set_range(
                mBuffer->range_offset() + mNALLengthSize + nal_size,
                mBuffer->range_length() - mNALLengthSize - nal_size);

        if (mBuffer->range_length() == 0) {
            mBuffer->release();
            mBuffer = NULL;
        }

        *out = clone;

        return OK;
    } else {
        // Whole NAL units are returned but each fragment is prefixed by
        // the start code (0x00 00 00 01).

        ssize_t num_bytes_read =
            mDataSource->readAt(offset, mSrcBuffer, size);

        if (num_bytes_read < (ssize_t)size) {
            mBuffer->release();
            mBuffer = NULL;

            return ERROR_IO;
        }

        uint8_t *dstData = (uint8_t *)mBuffer->data();
        size_t srcOffset = 0;
        size_t dstOffset = 0;

        while (srcOffset < size) {
            CHECK(srcOffset + mNALLengthSize <= size);
            size_t nalLength = parseNALSize(&mSrcBuffer[srcOffset]);
            srcOffset += mNALLengthSize;

            if (srcOffset + nalLength > size) {
                mBuffer->release();
                mBuffer = NULL;

                return ERROR_MALFORMED;
            }

            if (nalLength == 0) {
                continue;
            }

            CHECK(dstOffset + 4 <= mBuffer->size());

            dstData[dstOffset++] = 0;
            dstData[dstOffset++] = 0;
            dstData[dstOffset++] = 0;
            dstData[dstOffset++] = 1;
            memcpy(&dstData[dstOffset], &mSrcBuffer[srcOffset], nalLength);
            srcOffset += nalLength;
            dstOffset += nalLength;
        }
        CHECK_EQ(srcOffset, size);

        CHECK(mBuffer != NULL);
        mBuffer->set_range(0, dstOffset);
        mBuffer->meta_data()->clear();
        mBuffer->meta_data()->setInt64(
                kKeyTime, ((int64_t)dts * 1000000) / mTimescale);

        if (targetSampleTimeUs >= 0) {
            mBuffer->meta_data()->setInt64(
                    kKeyTargetTime, targetSampleTimeUs);
        }

        if (isSyncSample) {
            mBuffer->meta_data()->setInt32(kKeyIsSyncFrame, 1);
        }

        ++mCurrentSampleIndex;

        *out = mBuffer;
        mBuffer = NULL;

        return OK;
    }
}

static bool LegacySniffMPEG4(
        const sp<DataSource> &source, String8 *mimeType, float *confidence) {
    uint8_t header[8];

    ssize_t n = source->readAt(4, header, sizeof(header));
    if (n < (ssize_t)sizeof(header)) {
        return false;
    }

    if (!memcmp(header, "ftyp3gp", 7) || !memcmp(header, "ftypmp42", 8)
        || !memcmp(header, "ftyp3gr6", 8) || !memcmp(header, "ftyp3gs6", 8)
        || !memcmp(header, "ftyp3ge6", 8) || !memcmp(header, "ftyp3gg6", 8)
        || !memcmp(header, "ftypisom", 8) || !memcmp(header, "ftypM4V ", 8)
        || !memcmp(header, "ftypM4A ", 8) || !memcmp(header, "ftypf4v ", 8)
        || !memcmp(header, "ftypkddi", 8) || !memcmp(header, "ftypM4VP", 8)) {
        *mimeType = MEDIA_MIMETYPE_CONTAINER_MPEG4;
        *confidence = 0.4;

        return true;
    }

    return false;
}

static bool isCompatibleBrand(uint32_t fourcc) {
    static const uint32_t kCompatibleBrands[] = {
        FOURCC('i', 's', 'o', 'm'),
        FOURCC('i', 's', 'o', '2'),
        FOURCC('a', 'v', 'c', '1'),
        FOURCC('3', 'g', 'p', '4'),
        FOURCC('m', 'p', '4', '1'),
        FOURCC('m', 'p', '4', '2'),
    };

    for (size_t i = 0;
         i < sizeof(kCompatibleBrands) / sizeof(kCompatibleBrands[0]);
         ++i) {
        if (kCompatibleBrands[i] == fourcc) {
            return true;
        }
    }

    return false;
}

// Attempt to actually parse the 'ftyp' atom and determine if a suitable
// compatible brand is present.
static bool BetterSniffMPEG4(
        const sp<DataSource> &source, String8 *mimeType, float *confidence) {
    uint8_t header[12];
    if (source->readAt(0, header, 12) != 12
            || memcmp("ftyp", &header[4], 4)) {
        return false;
    }

    size_t atomSize = U32_AT(&header[0]);
    if (atomSize < 16 || (atomSize % 4) != 0) {
        return false;
    }

    bool success = false;
    if (isCompatibleBrand(U32_AT(&header[8]))) {
        success = true;
    } else {
        size_t numCompatibleBrands = (atomSize - 16) / 4;
        for (size_t i = 0; i < numCompatibleBrands; ++i) {
            uint8_t tmp[4];
            if (source->readAt(16 + i * 4, tmp, 4) != 4) {
                return false;
            }

            if (isCompatibleBrand(U32_AT(&tmp[0]))) {
                success = true;
                break;
            }
        }
    }

    if (!success) {
        return false;
    }

    *mimeType = MEDIA_MIMETYPE_CONTAINER_MPEG4;
    *confidence = 0.4f;

    return true;
}

bool SniffMPEG4(
        const sp<DataSource> &source, String8 *mimeType, float *confidence,
        sp<AMessage> *) {
    if (BetterSniffMPEG4(source, mimeType, confidence)) {
        return true;
    }

    if (LegacySniffMPEG4(source, mimeType, confidence)) {
        LOGW("Identified supported mpeg4 through LegacySniffMPEG4.");
        return true;
    }

    return false;
}

}  // namespace android