XINGSeeker.cpp revision b636abde14f2612ea236257846b9ab15d87d4623 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#define LOG_TAG "XINGSEEKER"
18#include <utils/Log.h>
19
20#include "include/XINGSeeker.h"
21#include "include/avc_utils.h"
22
23#include <media/stagefright/DataSource.h>
24#include <media/stagefright/Utils.h>
25
26namespace android {
27
28XINGSeeker::XINGSeeker()
29    : mDurationUs(-1),
30      mSizeBytes(0),
31      mEncoderDelay(0),
32      mEncoderPadding(0) {
33}
34
35bool XINGSeeker::getDuration(int64_t *durationUs) {
36    if (mDurationUs < 0) {
37        return false;
38    }
39
40    *durationUs = mDurationUs;
41
42    return true;
43}
44
45bool XINGSeeker::getOffsetForTime(int64_t *timeUs, off64_t *pos) {
46    if (mSizeBytes == 0 || !mTOCValid || mDurationUs < 0) {
47        return false;
48    }
49
50    float percent = (float)(*timeUs) * 100 / mDurationUs;
51    float fx;
52    if( percent <= 0.0f ) {
53        fx = 0.0f;
54    } else if( percent >= 100.0f ) {
55        fx = 256.0f;
56    } else {
57        int a = (int)percent;
58        float fa, fb;
59        if ( a == 0 ) {
60            fa = 0.0f;
61        } else {
62            fa = (float)mTOC[a-1];
63        }
64        if ( a < 99 ) {
65            fb = (float)mTOC[a];
66        } else {
67            fb = 256.0f;
68        }
69        fx = fa + (fb-fa)*(percent-a);
70    }
71
72    *pos = (int)((1.0f/256.0f)*fx*mSizeBytes) + mFirstFramePos;
73
74    return true;
75}
76
77// static
78sp<XINGSeeker> XINGSeeker::CreateFromSource(
79        const sp<DataSource> &source, off64_t first_frame_pos) {
80    sp<XINGSeeker> seeker = new XINGSeeker;
81
82    seeker->mFirstFramePos = first_frame_pos;
83
84    seeker->mSizeBytes = 0;
85    seeker->mTOCValid = false;
86    seeker->mDurationUs = 0;
87
88    uint8_t buffer[4];
89    int offset = first_frame_pos;
90    if (source->readAt(offset, &buffer, 4) < 4) { // get header
91        return NULL;
92    }
93    offset += 4;
94
95    int header = U32_AT(buffer);;
96    size_t xingframesize = 0;
97    int sampling_rate = 0;
98    int num_channels;
99    int samples_per_frame = 0;
100    if (!GetMPEGAudioFrameSize(header, &xingframesize, &sampling_rate, &num_channels,
101                               NULL, &samples_per_frame)) {
102        return NULL;
103    }
104    seeker->mFirstFramePos += xingframesize;
105
106    uint8_t version = (buffer[1] >> 3) & 3;
107
108    // determine offset of XING header
109    if(version & 1) { // mpeg1
110        if (num_channels != 1) offset += 32;
111        else offset += 17;
112    } else { // mpeg 2 or 2.5
113        if (num_channels != 1) offset += 17;
114        else offset += 9;
115    }
116
117    int xingbase = offset;
118
119    if (source->readAt(offset, &buffer, 4) < 4) { // XING header ID
120        return NULL;
121    }
122    offset += 4;
123    // Check XING ID
124    if ((buffer[0] != 'X') || (buffer[1] != 'i')
125                || (buffer[2] != 'n') || (buffer[3] != 'g')) {
126        if ((buffer[0] != 'I') || (buffer[1] != 'n')
127                    || (buffer[2] != 'f') || (buffer[3] != 'o')) {
128            return NULL;
129        }
130    }
131
132    if (source->readAt(offset, &buffer, 4) < 4) { // flags
133        return NULL;
134    }
135    offset += 4;
136    uint32_t flags = U32_AT(buffer);
137
138    if (flags & 0x0001) {  // Frames field is present
139        if (source->readAt(offset, buffer, 4) < 4) {
140             return NULL;
141        }
142        int32_t frames = U32_AT(buffer);
143        seeker->mDurationUs = (int64_t)frames * samples_per_frame * 1000000LL / sampling_rate;
144        offset += 4;
145    }
146    if (flags & 0x0002) {  // Bytes field is present
147        if (source->readAt(offset, buffer, 4) < 4) {
148            return NULL;
149        }
150        seeker->mSizeBytes = U32_AT(buffer);
151        offset += 4;
152    }
153    if (flags & 0x0004) {  // TOC field is present
154        if (source->readAt(offset + 1, seeker->mTOC, 99) < 99) {
155            return NULL;
156        }
157        seeker->mTOCValid = true;
158        offset += 100;
159    }
160
161#if 0
162    if (flags & 0x0008) {  // Quality indicator field is present
163        if (source->readAt(offset, buffer, 4) < 4) {
164            return NULL;
165        }
166        // do something with the quality indicator
167        offset += 4;
168    }
169
170    if (source->readAt(xingbase + 0xaf - 0x24, &buffer, 1) < 1) { // encoding flags
171        return false;
172    }
173
174    ALOGV("nogap preceding: %s, nogap continued in next: %s",
175              (buffer[0] & 0x80) ? "true" : "false",
176              (buffer[0] & 0x40) ? "true" : "false");
177#endif
178
179    if (source->readAt(xingbase + 0xb1 - 0x24, &buffer, 3) == 3) {
180        seeker->mEncoderDelay = (buffer[0] << 4) + (buffer[1] >> 4);
181        seeker->mEncoderPadding = ((buffer[1] & 0xf) << 8) + buffer[2];
182    }
183
184    return seeker;
185}
186
187int32_t XINGSeeker::getEncoderDelay() {
188    return mEncoderDelay;
189}
190
191int32_t XINGSeeker::getEncoderPadding() {
192    return mEncoderPadding;
193}
194
195}  // namespace android
196
197