Mpeg2 ts with VBI Data

rippi — Thu, 22 Nov 2007 08:12:43 GMT

I am trying to pack a H.264 video steam into a mpeg2 transport stream. It works very well. Now I have to add some further information (mata data) to that stream. My first idea was to put these information as vbi data. Unfortunately my application does not work properly and I cannot locate the errors. I also looked for some examples, but I could not find anything about vbi data in mpeg2ts. Can anybody help me with maybe some hints or examples?

Re: Mpeg2 ts with VBI Data

Ali_Gökalp_P_ — Thu, 22 Nov 2007 12:12:58 GMT

Same problem here, we 're also trying to pack MPEG4 video stream with private elementary stream that is neither video nor audio.We are trying to put into VBI_TRACK but we haven't succeeded yet.

Re: Mpeg2 ts with VBI Data

rippi — Mon, 03 Dec 2007 13:41:14 GMT

Hello,

there are some new ideas from me about transporting video and private elementary streams with Mpeg2Ts.

Now I can write the private streams as VBI-data (UMC::TrackType==UMC::TRACK_VBI_TXT) into the TS. Important to mention is, that the MPEG2TsChunkWriter does not work correctly for VBI-Data. So I have to overwrite the methods PrepareChunk() and WriteChunk():

Status VbiMPEG2TSChunkWriter::PrepareChunk(void) {
[...]
//old version
//if (m_uiStartIndicator && m_ESType != MPEG2MUX_ES_VBI_DATA)
//new version
if (m_uiStartIndicator) {
[...]
}

Status VbiMPEG2TSChunkWriter::WriteChunk(void) {
[...]
//old version
//if (m_uiStartIndicator && m_ESType != MPEG2MUX_ES_VBI_DATA)
//new version
if (m_uiStartIndicator) {
[...]
}

Now the Pes-Header will be written for VBI-data, too. This is necessary, because the Splitter looks for it while extracting the data.
The muxer has to be modified like this:

UMC::TrackParams &param = muxerParams->pTrackParams[trackNumberVbi];
param.type = UMC::VBI_TRACK;

//PID is a struct containing the private data
param.bufferParams.m_prefInputBufferSize = sizeof( PID );

//m_lpVbiParams is an object of a class, which is derived from UMC::BaseCodecParams
//info is an object from a class, which is derived from UMC::StreamInfo
param.info.undef = &m_lpVbiParams->info;

The data can be put into the TS like this:

//VbiData is derived from UMC::MediaData
VbiData mux_data( 2 * sizeof(PID) + 1 );
PID pid;
while (!bStopFlag) {
mux_data.setPrivateData(pid);
mux_data.SetDataSize(sizeof(PID));
memcpy(mux_data.GetDataPointer(), &mux_data.getMetadata(), sizeof(PID));

//IMPORTANT: Timestamps have to be set!
mux_data.SetTime(m_pts_Video_start, m_pts_Video_ende );
umcRes = m_lpMuxer->PutData(&mux_data, 1);
if (UMC::UMC_ERR_NOT_ENOUGH_BUFFER == umcRes){
vm_time_sleep(TIME_TO_SLEEP);
}
}
m_lpMuxer->PutEndOfStream(1);
m_lpMuxer->Flush();

When I tried to extract the VBI-data I realized, that the Demuxer has to be modified, too, because the UMC::Mpeg2PesParser is not able to ident ify VBI-data.
So I overwrote the method ParsePmtInfo():

Status VbiMpeg2PesParser::ParsePmtInfo(Mpeg2TsPmt &pmt) {
[...]
//old version
/*} else if (0x06 == pmt.pESs.uiType) {
// we should wait for decriptor to determine type
m_pInfo[iTrack]->m_Type = TRACK_UNKNOWN;
}*/
//new version
} else if (0x06 == pmt.pESs.uiType) {
//new for VBI
m_pInfo[iTrack]->m_Type = TRACK_VBI_TXT;
}
[...]
}

The next step is to define some rules for the UMC::ThreadedDemuxer and to start the demuxer:

UMC::Splitter m_pSplitter = new VbiThreadedDemuxer;
UMC::DemuxerParams m_lpDemuxerParams= new DemuxerParams;

m_lpDemuxerParams->m_pDataReader = m_pDataReader;
m_lpDemuxerParams->m_uiRules = 2;
m_lpDemuxerParams->m_pRules = new TrackRule[m_lpDemuxerParams->m_uiRules];

//one rule for video
m_lpDemuxerParams->m_pRules[0].m_TypeMask = TRACK_ANY_VIDEO;
m_lpDemuxerParams->m_pRules[0].m_iPID = -1;
m_lpDemuxerParams->m_pRules[0].m_iLimit = 1;
m_lpDemuxerParams->m_pRules[0].m_bValidAfterInit = true;

//one rule for vbi
m_lpDemuxerParams->m_pRules[1].m_TypeMask = TRACK_ANY_VBI;
m_lpDemuxerParams->m_pRules[1].m_iPID = -1;
m_lpDemuxerParams->m_pRules[1].m_iLimit = 1;
m_lpDemuxerParams->m_pRules[1].m_bValidAfterInit = true;

m_pSplitter->Init(*m_lpDemuxerParams);
m_pSplitter->Run();

Now the Splitter is able to identify VBI-data and videos and I could start to work on the data.
First look for the number of the VBI-track and save it in m_nVbiTrack:

Ipp32u i;
Ipp32u m_nVbiTrack;
UMC::SplitterInfo* pSplitterInfo = NULL;

m_pSplitter->GetInfo(&pSplitterInfo);

for (i=0; i< pSplitterInfo->m_nOfTracks; i++) {
if (pSplitterInfo->m_ppTrackInfo->m_isSelected) {
if (pSplitterInfo->m_ppTrackInfo->m_Type & UMC::TRACK_ANY_VBI) {
m_nVbiTrack = i;
vm_string_printf("VBI found... ");
}
}
}

Then extract the data of track number m_nVbiTrack out of the datastream:

UMC::MediaData vbiData;
PID pid;
size_t sizePid = sizeof(pid);

while(!bStopFlag) {
while(UMC::UMC_ERR_NOT_ENOUGH_DATA == m_pSplitter->GetNextData(&vbiData, m_nVbiTrack)) {
vm_time_sleep(5);
}
memcpy(&pid, vbiData.GetDataPointer(), sizePid);
pid.process();
}

Re: Mpeg2 ts with VBI Data

Ali_Gökalp_P_ — Fri, 14 Dec 2007 13:13:19 GMT

Thanks for the info... We've changed UMC in a different way , but this seems as a better one.

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