unsigned MPEG1or2VideoStreamParser::parsePictureHeader()
{
#ifdef DEBUG
fprintf(stderr, "parsing picture header\n");
#endif
// Note that we've already read the PICTURE_START_CODE
// Next, extract the temporal reference from the next 4 bytes:
unsigned next4Bytes = get4Bytes();
unsigned short temporal_reference = (next4Bytes & 0xFFC00000) >> (32 - 10);
unsigned char picture_coding_type = (next4Bytes & 0x00380000) >> 19;
#ifdef DEBUG
unsigned short vbv_delay = (next4Bytes & 0x0007FFF8) >> 3;
fprintf(stderr, "temporal_reference: %d, picture_coding_type: %d, vbv_delay: %d\n", temporal_reference, picture_coding_type, vbv_delay);
#endif
fSkippingCurrentPicture = fIFramesOnly && picture_coding_type != 1;
if (fSkippingCurrentPicture)
{
// Skip all bytes that we see, up until we reach a slice_start_code:
do
{
skipToNextCode(next4Bytes);
}
while (!isSliceStartCode(next4Bytes));
}
else
{
// Save the PICTURE_START_CODE that we've already read:
save4Bytes(PICTURE_START_CODE);
// Copy all bytes that we see, up until we reach a slice_start_code:
do
{
saveToNextCode(next4Bytes);
}
while (!isSliceStartCode(next4Bytes));
}
setParseState(PARSING_SLICE);
fCurrentSliceNumber = next4Bytes & 0xFF;
// Record the temporal reference:
fCurPicTemporalReference = temporal_reference;
// Compute this frame's timestamp:
usingSource()->computePresentationTime(fCurPicTemporalReference);
if (fSkippingCurrentPicture)
{
return parse(); // try again, until we get a non-skipped frame
}
else
{
return curFrameSize();
}
}
unsigned MPEG1or2VideoStreamParser
::parseVideoSequenceHeader(Boolean haveSeenStartCode) {
#ifdef DEBUG
fprintf(stderr, "parsing video sequence header\n");
#endif
unsigned first4Bytes;
if (!haveSeenStartCode) {
while ((first4Bytes = test4Bytes()) != VIDEO_SEQUENCE_HEADER_START_CODE) {
#ifdef DEBUG
fprintf(stderr, "ignoring non video sequence header: 0x%08x\n", first4Bytes);
#endif
get1Byte(); setParseState(PARSING_VIDEO_SEQUENCE_HEADER);
// ensures we progress over bad data
}
first4Bytes = get4Bytes();
} else {
// We've already seen the start code
first4Bytes = VIDEO_SEQUENCE_HEADER_START_CODE;
}
save4Bytes(first4Bytes);
// Next, extract the size and rate parameters from the next 8 bytes
unsigned paramWord1 = get4Bytes();
save4Bytes(paramWord1);
unsigned next4Bytes = get4Bytes();
#ifdef DEBUG
unsigned short horizontal_size_value = (paramWord1&0xFFF00000)>>(32-12);
unsigned short vertical_size_value = (paramWord1&0x000FFF00)>>8;
unsigned char aspect_ratio_information = (paramWord1&0x000000F0)>>4;
#endif
unsigned char frame_rate_code = (paramWord1&0x0000000F);
usingSource()->fFrameRate = frameRateFromCode[frame_rate_code];
#ifdef DEBUG
unsigned bit_rate_value = (next4Bytes&0xFFFFC000)>>(32-18);
unsigned vbv_buffer_size_value = (next4Bytes&0x00001FF8)>>3;
fprintf(stderr, "horizontal_size_value: %d, vertical_size_value: %d, aspect_ratio_information: %d, frame_rate_code: %d (=>%f fps), bit_rate_value: %d (=>%d bps), vbv_buffer_size_value: %d\n", horizontal_size_value, vertical_size_value, aspect_ratio_information, frame_rate_code, usingSource()->fFrameRate, bit_rate_value, bit_rate_value*400, vbv_buffer_size_value);
#endif
// Now, copy all bytes that we see, up until we reach a GROUP_START_CODE
// or a PICTURE_START_CODE:
do {
saveToNextCode(next4Bytes);
} while (next4Bytes != GROUP_START_CODE && next4Bytes != PICTURE_START_CODE);
setParseState((next4Bytes == GROUP_START_CODE)
? PARSING_GOP_HEADER_SEEN_CODE : PARSING_PICTURE_HEADER);
// Compute this frame's timestamp by noting how many pictures we've seen
// since the last GOP header:
usingSource()->computePresentationTime(fPicturesSinceLastGOP);
// Save this video_sequence_header, in case we need to insert a copy
// into the stream later:
saveCurrentVSH();
return curFrameSize();
}
unsigned MPEG4VideoStreamParser
::parseVisualObjectSequence(Boolean haveSeenStartCode) {
#ifdef DEBUG
fprintf(stderr, "parsing VisualObjectSequence\n");
#endif
usingSource()->startNewConfig();
u_int32_t first4Bytes;
if (!haveSeenStartCode) {
while ((first4Bytes = test4Bytes()) != VISUAL_OBJECT_SEQUENCE_START_CODE) {
#ifdef DEBUG
fprintf(stderr, "ignoring non VS header: 0x%08x\n", first4Bytes);
#endif
get1Byte(); setParseState(PARSING_VISUAL_OBJECT_SEQUENCE);
// ensures we progress over bad data
}
first4Bytes = get4Bytes();
} else {
// We've already seen the start code
first4Bytes = VISUAL_OBJECT_SEQUENCE_START_CODE;
}
save4Bytes(first4Bytes);
// The next byte is the "profile_and_level_indication":
u_int8_t pali = get1Byte();
#ifdef DEBUG
fprintf(stderr, "profile_and_level_indication: %02x\n", pali);
#endif
saveByte(pali);
usingSource()->fProfileAndLevelIndication = pali;
// Now, copy all bytes that we see, up until we reach
// a VISUAL_OBJECT_START_CODE:
u_int32_t next4Bytes = get4Bytes();
while (next4Bytes != VISUAL_OBJECT_START_CODE) {
saveToNextCode(next4Bytes);
}
setParseState(PARSING_VISUAL_OBJECT);
// Compute this frame's presentation time:
usingSource()->computePresentationTime(fTotalTicksSinceLastTimeCode);
// This header forms part of the 'configuration' information:
usingSource()->appendToNewConfig(fStartOfFrame, curFrameSize());
return curFrameSize();
}
unsigned MPEG1or2VideoStreamParser::parseSlice()
{
// Note that we've already read the slice_start_code:
unsigned next4Bytes = PICTURE_START_CODE | fCurrentSliceNumber;
#ifdef DEBUG_SLICE
fprintf(stderr, "parsing slice: 0x%08x\n", next4Bytes);
#endif
if (fSkippingCurrentPicture)
{
// Skip all bytes that we see, up until we reach a code of some sort:
skipToNextCode(next4Bytes);
}
else
{
// Copy all bytes that we see, up until we reach a code of some sort:
saveToNextCode(next4Bytes);
}
// The next thing to parse depends on the code that we just saw:
if (isSliceStartCode(next4Bytes)) // common case
{
setParseState(PARSING_SLICE);
fCurrentSliceNumber = next4Bytes & 0xFF;
}
else
{
// Because we don't see any more slices, we are assumed to have ended
// the current picture:
++fPicturesSinceLastGOP;
++usingSource()->fPictureCount;
usingSource()->fPictureEndMarker = True; // HACK #####
switch (next4Bytes)
{
case SEQUENCE_END_CODE:
{
setParseState(PARSING_VIDEO_SEQUENCE_HEADER);
break;
}
case VIDEO_SEQUENCE_HEADER_START_CODE:
{
setParseState(PARSING_VIDEO_SEQUENCE_HEADER_SEEN_CODE);
break;
}
case GROUP_START_CODE:
{
setParseState(PARSING_GOP_HEADER_SEEN_CODE);
break;
}
case PICTURE_START_CODE:
{
setParseState(PARSING_PICTURE_HEADER);
break;
}
default:
{
usingSource()->envir() << "MPEG1or2VideoStreamParser::parseSlice(): Saw unexpected code "
<< (void *)next4Bytes << "\n";
setParseState(PARSING_SLICE); // the safest way to recover...
break;
}
}
}
// Compute this frame's timestamp:
usingSource()->computePresentationTime(fCurPicTemporalReference);
if (fSkippingCurrentPicture)
{
return parse(); // try again, until we get a non-skipped frame
}
else
{
return curFrameSize();
}
}
unsigned MPEG1or2VideoStreamParser::parseGOPHeader(Boolean haveSeenStartCode)
{
// First check whether we should insert a previously-saved
// 'video_sequence_header' here:
if (needToUseSavedVSH()) return useSavedVSH();
#ifdef DEBUG
fprintf(stderr, "parsing GOP header\n");
#endif
unsigned first4Bytes;
if (!haveSeenStartCode)
{
while ((first4Bytes = test4Bytes()) != GROUP_START_CODE)
{
#ifdef DEBUG
fprintf(stderr, "ignoring non GOP start code: 0x%08x\n", first4Bytes);
#endif
get1Byte();
setParseState(PARSING_GOP_HEADER);
// ensures we progress over bad data
}
first4Bytes = get4Bytes();
}
else
{
// We've already seen the GROUP_START_CODE
first4Bytes = GROUP_START_CODE;
}
save4Bytes(first4Bytes);
// Next, extract the (25-bit) time code from the next 4 bytes:
unsigned next4Bytes = get4Bytes();
unsigned time_code = (next4Bytes & 0xFFFFFF80) >> (32 - 25);
#if defined(DEBUG) || defined(DEBUG_TIMESTAMPS)
Boolean drop_frame_flag = (time_code & 0x01000000) != 0;
#endif
unsigned time_code_hours = (time_code & 0x00F80000) >> 19;
unsigned time_code_minutes = (time_code & 0x0007E000) >> 13;
unsigned time_code_seconds = (time_code & 0x00000FC0) >> 6;
unsigned time_code_pictures = (time_code & 0x0000003F);
#if defined(DEBUG) || defined(DEBUG_TIMESTAMPS)
fprintf(stderr, "time_code: 0x%07x, drop_frame %d, hours %d, minutes %d, seconds %d, pictures %d\n", time_code, drop_frame_flag, time_code_hours, time_code_minutes, time_code_seconds, time_code_pictures);
#endif
#ifdef DEBUG
Boolean closed_gop = (next4Bytes & 0x00000040) != 0;
Boolean broken_link = (next4Bytes & 0x00000020) != 0;
fprintf(stderr, "closed_gop: %d, broken_link: %d\n", closed_gop, broken_link);
#endif
// Now, copy all bytes that we see, up until we reach a PICTURE_START_CODE:
do
{
saveToNextCode(next4Bytes);
}
while (next4Bytes != PICTURE_START_CODE);
// Record the time code:
usingSource()->setTimeCode(time_code_hours, time_code_minutes,
time_code_seconds, time_code_pictures,
fPicturesSinceLastGOP);
fPicturesSinceLastGOP = 0;
// Compute this frame's timestamp:
usingSource()->computePresentationTime(0);
setParseState(PARSING_PICTURE_HEADER);
return curFrameSize();
}
