RE: helix metadata

Erwan,

[Again, please remember to copy a helix mailing list.]

>   For that reason, I want to know specifically how helix works. That's to
>say what happens when a stream is arriving, how does Helix Client parses the
>streams, how does it get, retrieve the information to play back the stream,
>how the renderer can access to these information.

Here's a good place to start:

https://helix-client.helixcommunity.org/Architecture

>   I know that, when a stream is arriving Helix permits to abstract UDP, TCP
>protocols or local files. Then it gets the mime type thanks to the
>recognizer. This permits to parse the streams in InitializeRenderer(),
>comparing the mime type of each renderer with the mime type of the stream.
>Concerning the structure that contains the metadata, I don't really know how
>it works. I know metadata are retrieved in CreateStreamHeader(). Then
>they're put in a stream header. Then, you told me a SDP file was created to
>put these information and finally a IHXRegistry. I'd like to know where does
>this happen in the source code.
>

There are several different paths depending on whether playback is via
RTSP, HTTP, or local file playback. Which one will you be using?

Eric

=======================================
Eric Hyche ([email protected])
Principal Engineer
RealNetworks, Inc.


>-----Original Message-----
>From: Erwan Gouyette [mailto:[email protected]]
>Sent: Wednesday, May 06, 2009 9:04 AM
>To: [email protected]
>Subject: RE: [Helix-client-dev] helix metadata
>
>
>Hi! Thanks for replying so quickly.
>
>-->Do you want to playback the media, or just examine the metadata?
>
>   The thing is I already have a solution to read streams in a set top box.
>But the way the parsing of streams is done is no good and Helix Client does
>that very well. So I'd like to integrate this solution.
>   For that reason, I want to know specifically how helix works. That's to
>say what happens when a stream is arriving, how does Helix Client parses the
>streams, how does it get, retrieve the information to play back the stream,
>how the renderer can access to these information.
>
>   I know that, when a stream is arriving Helix permits to abstract UDP, TCP
>protocols or local files. Then it gets the mime type thanks to the
>recognizer. This permits to parse the streams in InitializeRenderer(),
>comparing the mime type of each renderer with the mime type of the stream.
>Concerning the structure that contains the metadata, I don't really know how
>it works. I know metadata are retrieved in CreateStreamHeader(). Then
>they're put in a stream header. Then, you told me a SDP file was created to
>put these information and finally a IHXRegistry. I'd like to know where does
>this happen in the source code.
>
>Hope I'm not wrong, thanks a lot,
>
>Erwan
>
>
>
>-----Message d'origine-----
>De : Eric Hyche [mailto:[email protected]]
>Envoyé : mercredi 6 mai 2009 14:01
>À : 'Erwan Gouyette'
>Cc : [email protected]
>Objet : RE: [Helix-client-dev] helix metadata
>
>Erwan,
>
>[Please copy a Helix mailing list when you send me email about Helix.
>Sometimes I won't be able to get to support email like this
>for a while and other engineers on the list may be able to help you sooner.]
>
>>--> I'm interested in retrieving metadata that indicate how to play the
>>stream. So, if I'm not wrong, these metadata are retrieved in the stream
>>header IHXValues* pHeader, during step 8) CreateStreamHeader(). This is
>done
>>by the File_Format. Then the stream header pHeader is returned to the
>server
>>in step 9) StreamHeaderReady(). In this same step the SDP file is created
>>but I can't see in which call... Is the stream info file the SDP file?
>>Finally I don't know where all informations are put inside a IHXRegistry.
>>
>
>Do you want to playback the media, or just examine the metadata? I was
>assuming
>you wanted to playback AND observe metadata. If you just want to look at
>the metadata, then there is a simpler way of doing that: take a look
>at the sample code in datatype/tools/dtdriver/samples/metadata. This uses
>the dtdriver framework.
>
>>--> All this concerns the playback of local files. Is this the same for
>>streaming from any server? Cause this is what I'm really concerned about.
>>
>
>Yes - this works for local and streaming cases.
>
>Eric
>
>=======================================
>Eric Hyche ([email protected])
>Principal Engineer
>RealNetworks, Inc.
>
>
>>-----Original Message-----
>>From: Erwan Gouyette [mailto:[email protected]]
>>Sent: Wednesday, May 06, 2009 5:09 AM
>>To: [email protected]
>>Subject: RE: [Helix-client-dev] helix metadata
>>
>>
>>
>>I found out that :
>>
>>*************************************************************
>>  1)In HXFileSource::InitDone (HX_RESULT	 status), there's :
>>
>>    m_pFFObject->GetFileHeader();
>>
>>
>>  2)In CAACFileFormat::GetFileHeader(), there's :
>>
>>    m_pFileObject->Seek( 0, FALSE);
>>
>>
>>  3)In HXFileSource::FileHeaderReady ( HX_RESULT status, IHXValues*
>>pHeader), there's :
>>
>>    ContinueWithFileHeader(status, pHeader);
>>
>>
>>  4)In HXFileSource::ContinueWithFileHeader(HX_RESULT status, IHXValues*
>>pHeader), there's :
>>
>>     ProcessFileHeader();
>>
>>
>>  5)In HXFileSource::ProcessFileHeader(void), there's :
>>
>>    HXSource::ProcessFileHeader();
>>    and
>>    m_pFFObject->GetStreamHeader(i);
>>
>>
>>  6)In HXSource::ProcessFileHeader(void), there's :
>>
>>    IHXBuffer*  pTitle = NULL;
>>    IHXBuffer*  pAuthor = NULL;
>>    IHXBuffer*  pCopyright = NULL;
>>    IHXBuffer*  pAbstract = NULL;
>>    IHXBuffer*  pDescription = NULL;
>>    IHXBuffer*  pLicenseInfo = NULL;
>>    IHXBuffer*  pKeywords = NULL;
>>    IHXValues*  pValues = NULL;
>>    IHXValues*  pMetaInfo = NULL;
>>    …
>>    pValues->GetPropertyBuffer("Title", pTitle);
>>    pValues->GetPropertyBuffer("Author", pAuthor);
>>    pValues->GetPropertyBuffer("Copyright", pCopyright);
>>    pValues->GetPropertyBuffer("Abstract", pAbstract);
>>    pValues->GetPropertyBuffer("Description", pDescription);
>>    pValues->GetPropertyBuffer("Keywords", pKeywords);
>>    …
>>    if (!pTitle)        m_pFileHeader->GetPropertyBuffer("Title", pTitle);
>>    if (!pAuthor)       m_pFileHeader->GetPropertyBuffer("Author",
>pAuthor);
>>    if (!pCopyright)    m_pFileHeader->GetPropertyBuffer("Copyright",
>>pCopyright);
>>    if (!pDescription)  m_pFileHeader->GetPropertyCString("Description",
>>pDescription);
>>    if (!pAbstract)     m_pFileHeader->GetPropertyCString("Abstract",
>>pAbstract);
>>    if (!pKeywords)     m_pFileHeader->GetPropertyCString("Keywords",
>>pKeywords);
>>    …
>>    if (pTitle)        pMetaInfo->SetPropertyBuffer("Title", pTitle);
>>    if (pAuthor)       pMetaInfo->SetPropertyBuffer("Author", pAuthor);
>>    if (pCopyright)    pMetaInfo->SetPropertyBuffer("Copyright",
>>pCopyright);
>>    if (pDescription)  pMetaInfo->SetPropertyBuffer("Description",
>>pDescription);
>>    if (pAbstract)     pMetaInfo->SetPropertyBuffer("Abstract", pAbstract);
>>    if (pKeywords)     pMetaInfo->SetPropertyBuffer("Keywords", pKeywords);
>>
>>
>>  7)In CAACFileFormat::GetStreamHeader(UINT16 unStreamNumber, there's :
>>
>>    retVal = CreateStreamHeader(pBuf);
>>
>>
>>  8)In CAACFileFormat::CreateStreamHeader(IHXBuffer * pAACFrame), there's :
>>
>>    pHdr->SetPropertyULONG32("AvgBitRate", m_ulAvgBitRate);
>>    …
>>    retVal = m_pFileType->UpdateStreamHeader(pHdr, pAACFrame, m_pContext);
>>    …
>>    retVal = m_pPayloadFormat->SetStreamHeader(pHdr);
>>    …
>>    retVal = m_pFormatResponse->StreamHeaderReady(retVal, pHdr);
>>
>>
>>  9)In HXFileSource::StreamHeaderReady(HX_RESULT status, IHXValues*
>>pHeader), ther's :
>>
>>    STREAM_INFO*    pStreamInfo = NULL;
>>    …
>>    status = HandleSDPData(pHeader);
>>    …
>>    StreamHeaderReadyExt(pHeader);
>>    …
>>    return ProcessStreamHeaders(pHeader, pStreamInfo);
>>
>>
>>  10)In HXFileSource::ProcessStreamHeaders(IHXValues* pHeader,
>STREAM_INFO*&
>>pStreamInfo), there's :
>>
>>    theErr = HXSource::ProcessStreamHeaders(pHeader, pStreamInfo);
>>
>>
>>  11)In HXSource::ProcessStreamHeaders(IHXValues* pHeader, STREAM_INFO*&
>>pStreamInfo), there's :
>>
>>    pHeader->GetPropertyULONG32("StreamNumber",     ulStreamNumber);
>>    pHeader->GetPropertyULONG32("AvgBitRate",       ulAvgBitRate);
>>    pHeader->GetPropertyULONG32("MaxBitRate",       ulMaxBitRate);
>>    pHeader->GetPropertyULONG32("AvgPacketSize",    ulAvgPacketSize);
>>    pHeader->GetPropertyULONG32("Predata",          ulPredata);
>>    pHeader->GetPropertyULONG32("Duration",         ulDuration);
>>    …
>>    pStreamInfo->BufferingState().OnStreamHeader(
>>    ulStreamNumber,
>>    ulPreroll,
>>    ulPredata,
>>    GetHeaderBOOL(pHeader, "PreDataAtStart"),
>>    GetHeaderBOOL(pHeader, "PreDataAfterSeek"),
>>    GetHeaderBOOL(pHeader, "PrerollAtStart"),
>>    GetHeaderBOOL(pHeader, "PrerollAfterSeek"),
>>    ulAvgBitRate,
>>    ulMaxBitRate,
>>    pMimeType);
>>**********************************************************************
>>
>>
>>--> I'm interested in retrieving metadata that indicate how to play the
>>stream. So, if I'm not wrong, these metadata are retrieved in the stream
>>header IHXValues* pHeader, during step 8) CreateStreamHeader(). This is
>done
>>by the File_Format. Then the stream header pHeader is returned to the
>server
>>in step 9) StreamHeaderReady(). In this same step the SDP file is created
>>but I can't see in which call... Is the stream info file the SDP file?
>>Finally I don't know where all informations are put inside a IHXRegistry.
>>
>>--> All this concerns the playback of local files. Is this the same for
>>streaming from any server? Cause this is what I'm really concerned about.
>>
>>Thanks a lot,
>>
>>Erwan
>>
>>
>>
>>-----Message d'origine-----
>>De : Eric Hyche [mailto:[email protected]]
>>Envoyé : mardi 21 avril 2009 18:18
>>À : 'Erwan Gouyette'
>>Objet : RE: [Helix-client-dev] helix metadata
>>
>>In general it works like this:
>>
>>- file format plugin on the server reads the meta-data out of the media
>>  file and puts it in a file header IHXValues which it returns to the
>>  server in a IHXFormatResponse::FileHeaderReady() call.
>>- Server takes the meta-data from the file header IHXValues and puts
>>  it into the SDP which is provided in the RTSP DESCRIBE response.
>>- client reads the SDP in the RTSP DESCRIBE response and populates
>>  the IHXRegistry with the appropriate meta-data, so that other components
>>  (or the application) can read the meta-data from there.
>>
>>Eric
>>
>>=======================================
>>Eric Hyche ([email protected])
>>Principal Engineer
>>RealNetworks, Inc.
>>
>>
>>>-----Original Message-----
>>>From: Erwan Gouyette [mailto:[email protected]]
>>>Sent: Tuesday, April 21, 2009 11:24 AM
>>>To: [email protected]
>>>Subject: RE: [Helix-client-dev] helix metadata
>>>
>>>Ok, thank you. But what I don't understand is when and how helix client
>>>retrieves the metadata that are coming in a stream. I guess that inside
>>data
>>>received and stocked in a buffer, it has to retrieve metadata to make the
>>>renderer work properly. So, in the source code, where does this happen
>>>(HXFileSource::Setup())? I thought a stream header was created and
>metadata
>>>were put inside. Then renderer could access to data through the stream
>>>header pointer. Apologies for any inconveniences. Thanks for helping me,
>>>
>>>Erwan
>>>
>>>PS: I tried several times and spent hours to build splay but I just can't
>>>get through. I could retrieve all sources but I can't go further because
>of
>>>"authenticity of host can't be established". I don't understand why, it
>>>makes no sense. But maybe you could indicate me where to look for a debug
>>>trace... Thanks
>>>
>>>
>>>-----Message d'origine-----
>>>De : Eric Hyche [mailto:[email protected]]
>>>Envoyé : mardi 21 avril 2009 15:27
>>>À : 'Erwan Gouyette'; [email protected]
>>>Objet : RE: [Helix-client-dev] helix metadata
>>>
>>>The metadata for the currently playing clip is stored in the Helix
>>>IHXRegistry. For an example of this, build splay and run it with
>>>the -a option. Every 1s or so it will print out its entire registry tree,
>>>and you should be able to find the relevant metadata
>>>there.
>>>
>>>Eric
>>>
>>>=======================================
>>>Eric Hyche ([email protected])
>>>Principal Engineer
>>>RealNetworks, Inc.
>>>
>>>
>>>>-----Original Message-----
>>>>From: [email protected]
>>>[mailto:[email protected]]
>>>>On Behalf Of Erwan Gouyette
>>>>Sent: Monday, April 20, 2009 3:54 AM
>>>>To: [email protected]
>>>>Subject: [Helix-client-dev] helix metadata
>>>>
>>>>Hello, I'd like to know where (in which function) helix client retrieve
>>>metadata about the stream it's
>>>>playing?  Thanks,
>>>>
>>>>
>>>>
>>>>Erwan
>>>
>>
>