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Clean up MP3Extractor code and fixes a bug that miscalculated the position of the header by a few bytes whenever we read in more data.

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This commit is contained in:
Andreas Huber
2009-07-17 08:28:57 -07:00
parent 4a967dabc3
commit 2e337a4e4b
1 changed files with 37 additions and 32 deletions
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69
media/libstagefright/MP3Extractor.cpp
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@@ -73,6 +73,8 @@ static bool get_mp3_frame_size(
if (bitrate_index == 0 || bitrate_index == 0x0f) {
// Disallow "free" bitrate.
LOGE("We disallow 'free' bitrate for now.");
return false;
}
@@ -174,7 +176,7 @@ static bool Resync(
const size_t kMaxFrameSize = 4096;
uint8_t *buffer = new uint8_t[kMaxFrameSize];
off_t pos = *inout_pos;
off_t pos = *inout_pos - kMaxFrameSize;
size_t buffer_offset = kMaxFrameSize;
size_t buffer_length = kMaxFrameSize;
bool valid = false;
@@ -184,7 +186,7 @@ static bool Resync(
break;
}
pos += buffer_length;
pos += buffer_offset;
if (pos >= *inout_pos + 128 * 1024) {
// Don't scan forever.
@@ -217,42 +219,45 @@ static bool Resync(
size_t frame_size;
int sample_rate, num_channels, bitrate;
if (get_mp3_frame_size(header, &frame_size,
if (!get_mp3_frame_size(header, &frame_size,
&sample_rate, &num_channels, &bitrate)) {
LOGV("found possible 1st frame at %ld", pos + buffer_offset);
++buffer_offset;
continue;
}
// We found what looks like a valid frame,
// now find its successors.
LOGV("found possible 1st frame at %ld", pos + buffer_offset);
off_t test_pos = pos + buffer_offset + frame_size;
// We found what looks like a valid frame,
// now find its successors.
valid = true;
for (int j = 0; j < 3; ++j) {
uint8_t tmp[4];
if (source->read_at(test_pos, tmp, 4) < 4) {
valid = false;
break;
}
uint32_t test_header = U32_AT(tmp);
off_t test_pos = pos + buffer_offset + frame_size;
LOGV("subsequent header is %08x", test_header);
if ((test_header & kMask) != (header & kMask)) {
valid = false;
break;
}
size_t test_frame_size;
if (!get_mp3_frame_size(test_header, &test_frame_size)) {
valid = false;
break;
}
LOGV("found subsequent frame #%d at %ld", j + 2, test_pos);
test_pos += test_frame_size;
valid = true;
for (int j = 0; j < 3; ++j) {
uint8_t tmp[4];
if (source->read_at(test_pos, tmp, 4) < 4) {
valid = false;
break;
}
uint32_t test_header = U32_AT(tmp);
LOGV("subsequent header is %08x", test_header);
if ((test_header & kMask) != (header & kMask)) {
valid = false;
break;
}
size_t test_frame_size;
if (!get_mp3_frame_size(test_header, &test_frame_size)) {
valid = false;
break;
}
LOGV("found subsequent frame #%d at %ld", j + 2, test_pos);
test_pos += test_frame_size;
}
if (valid) {