xref: /frameworks/av/media/libstagefright/timedtext/TimedTextSRTSource.cpp

 /*
 * Copyright (C) 2012 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_NDEBUG 0
#define LOG_TAG "TimedTextSRTSource"
#include <utils/Log.h>

#include <binder/Parcel.h>
#include <media/stagefright/foundation/ADebug.h>  // for CHECK_xx
#include <media/stagefright/foundation/AString.h>
#include <media/stagefright/DataSource.h>
#include <media/stagefright/MediaDefs.h>  // for MEDIA_MIMETYPE_xxx
#include <media/stagefright/MediaErrors.h>
#include <media/stagefright/MediaSource.h>
#include <media/stagefright/MetaData.h>

#include "TimedTextSRTSource.h"
#include "TextDescriptions.h"

namespace android {

TimedTextSRTSource::TimedTextSRTSource(const sp<DataSource>& dataSource)
        : mSource(dataSource),
          mMetaData(new MetaData),
          mIndex(0) {
    // TODO: Need to detect the language, because SRT doesn't give language
    // information explicitly.
    mMetaData->setCString(kKeyMediaLanguage, "und");
}

TimedTextSRTSource::~TimedTextSRTSource() {
}

status_t TimedTextSRTSource::start() {
    status_t err = scanFile();
    if (err != OK) {
        reset();
    }
    return err;
}

void TimedTextSRTSource::reset() {
    mTextVector.clear();
    mIndex = 0;
}

status_t TimedTextSRTSource::stop() {
    reset();
    return OK;
}

status_t TimedTextSRTSource::read(
        int64_t *startTimeUs,
        int64_t *endTimeUs,
        Parcel *parcel,
        const MediaSource::ReadOptions *options) {
    AString text;
    status_t err = getText(options, &text, startTimeUs, endTimeUs);
    if (err != OK) {
        return err;
    }

    CHECK_GE(*startTimeUs, 0);
    extractAndAppendLocalDescriptions(*startTimeUs, text, parcel);
    return OK;
}

sp<MetaData> TimedTextSRTSource::getFormat() {
    return mMetaData;
}

status_t TimedTextSRTSource::scanFile() {
    off64_t offset = 0;
    int64_t startTimeUs;
    bool endOfFile = false;

    while (!endOfFile) {
        TextInfo info;
        status_t err = getNextSubtitleInfo(&offset, &startTimeUs, &info);
        switch (err) {
            case OK:
                mTextVector.add(startTimeUs, info);
                break;
            case ERROR_END_OF_STREAM:
                endOfFile = true;
                break;
            default:
                return err;
        }
    }
    if (mTextVector.isEmpty()) {
        return ERROR_MALFORMED;
    }
    return OK;
}

/* SRT format:
 *   Subtitle number
 *   Start time --> End time
 *   Text of subtitle (one or more lines)
 *   Blank lines
 *
 * .srt file example:
 * 1
 * 00:00:20,000 --> 00:00:24,400
 * Altocumulus clouds occr between six thousand
 *
 * 2
 * 00:00:24,600 --> 00:00:27,800
 * and twenty thousand feet above ground level.
 */
status_t TimedTextSRTSource::getNextSubtitleInfo(
          off64_t *offset, int64_t *startTimeUs, TextInfo *info) {
    AString data;
    status_t err;

    // To skip blank lines.
    do {
        if ((err = readNextLine(offset, &data)) != OK) {
            return err;
        }
        data.trim();
    } while (data.empty());

    // Just ignore the first non-blank line which is subtitle sequence number.
    if ((err = readNextLine(offset, &data)) != OK) {
        return err;
    }
    int hour1, hour2, min1, min2, sec1, sec2, msec1, msec2;
    // the start time format is: hours:minutes:seconds,milliseconds
    // 00:00:24,600 --> 00:00:27,800
    if (sscanf(data.c_str(), "%02d:%02d:%02d,%03d --> %02d:%02d:%02d,%03d",
               &hour1, &min1, &sec1, &msec1, &hour2, &min2, &sec2, &msec2) != 8) {
        return ERROR_MALFORMED;
    }

    *startTimeUs = ((hour1 * 3600 + min1 * 60 + sec1) * 1000 + msec1) * 1000ll;
    info->endTimeUs = ((hour2 * 3600 + min2 * 60 + sec2) * 1000 + msec2) * 1000ll;
    if (info->endTimeUs <= *startTimeUs) {
        return ERROR_MALFORMED;
    }

    info->offset = *offset;
    bool needMoreData = true;
    while (needMoreData) {
        if ((err = readNextLine(offset, &data)) != OK) {
            if (err == ERROR_END_OF_STREAM) {
                break;
            } else {
                return err;
            }
        }

        data.trim();
        if (data.empty()) {
            // it's an empty line used to separate two subtitles
            needMoreData = false;
        }
    }
    info->textLen = *offset - info->offset;
    return OK;
}

status_t TimedTextSRTSource::readNextLine(off64_t *offset, AString *data) {
    data->clear();
    while (true) {
        ssize_t readSize;
        char character;
        if ((readSize = mSource->readAt(*offset, &character, 1)) < 1) {
            if (readSize == 0) {
                return ERROR_END_OF_STREAM;
            }
            return ERROR_IO;
        }

        (*offset)++;

        // a line could end with CR, LF or CR + LF
        if (character == 10) {
            break;
        } else if (character == 13) {
            if ((readSize = mSource->readAt(*offset, &character, 1)) < 1) {
                if (readSize == 0) {  // end of the stream
                    return OK;
                }
                return ERROR_IO;
            }

            (*offset)++;
            if (character != 10) {
                (*offset)--;
            }
            break;
        }
        data->append(character);
    }
    return OK;
}

status_t TimedTextSRTSource::getText(
        const MediaSource::ReadOptions *options,
        AString *text, int64_t *startTimeUs, int64_t *endTimeUs) {
    if (mTextVector.size() == 0) {
        return ERROR_END_OF_STREAM;
    }
    text->clear();
    int64_t seekTimeUs;
    MediaSource::ReadOptions::SeekMode mode;
    if (options != NULL && options->getSeekTo(&seekTimeUs, &mode)) {
        int64_t lastEndTimeUs =
                mTextVector.valueAt(mTextVector.size() - 1).endTimeUs;
        if (seekTimeUs < 0) {
            return ERROR_OUT_OF_RANGE;
        } else if (seekTimeUs >= lastEndTimeUs) {
            return ERROR_END_OF_STREAM;
        } else {
            // binary search
            size_t low = 0;
            size_t high = mTextVector.size() - 1;
            size_t mid = 0;

            while (low <= high) {
                mid = low + (high - low)/2;
                int diff = compareExtendedRangeAndTime(mid, seekTimeUs);
                if (diff == 0) {
                    break;
                } else if (diff < 0) {
                    low = mid + 1;
                } else {
                    high = mid - 1;
                }
            }
            mIndex = mid;
        }
    }

    if (mIndex >= mTextVector.size()) {
        return ERROR_END_OF_STREAM;
    }

    const TextInfo &info = mTextVector.valueAt(mIndex);
    *startTimeUs = mTextVector.keyAt(mIndex);
    *endTimeUs = info.endTimeUs;
    mIndex++;

    char *str = new char[info.textLen];
    if (mSource->readAt(info.offset, str, info.textLen) < info.textLen) {
        delete[] str;
        return ERROR_IO;
    }
    text->append(str, info.textLen);
    delete[] str;
    return OK;
}

status_t TimedTextSRTSource::extractAndAppendLocalDescriptions(
        int64_t timeUs, const AString &text, Parcel *parcel) {
    const void *data = text.c_str();
    size_t size = text.size();
    int32_t flag = TextDescriptions::LOCAL_DESCRIPTIONS |
                   TextDescriptions::OUT_OF_BAND_TEXT_SRT;

    if (size > 0) {
        return TextDescriptions::getParcelOfDescriptions(
                (const uint8_t *)data, size, flag, timeUs / 1000, parcel);
    }
    return OK;
}

int TimedTextSRTSource::compareExtendedRangeAndTime(size_t index, int64_t timeUs) {
    CHECK_LT(index, mTextVector.size());
    int64_t endTimeUs = mTextVector.valueAt(index).endTimeUs;
    int64_t startTimeUs = (index > 0) ?
            mTextVector.valueAt(index - 1).endTimeUs : 0;
    if (timeUs >= startTimeUs && timeUs < endTimeUs) {
        return 0;
    } else if (endTimeUs <= timeUs) {
        return -1;
    } else {
        return 1;
    }
}

}  // namespace android