GNOME Bugzilla – Bug 588261
[mpegtsmux] allow the PCR to be in a PID of its own
Last modified: 2011-09-13 09:21:26 UTC
I'd like to open a discussion on the feature of having the PCR in a distinct stream rather than associated to an existing audio or video stream for a given program. The Transport Stream standard (ISO/IEC 13818) allows both use cases, but I've observed that most professional video broadcasting equipment will separate the PCR from the PES streams and put it in a distinct PID. Maybe some playback devices only support this presentation model. I've analyzed the tsmux library used in the mpegtsmux plugin and it looks like the PCR is solidly related to the PES, so this feature isn't a simple matter of creating a new blank PID and setting it as PCR. In fact, the library doesn't allow creating a new PID that doesn't have a valid stream type. In order to implement this without rewriting the whole lib, I think we could write a PRC stream creator and make some sort of association between one of the PES and this distinct PCR stream so that the existing PCR mechanism continues to work.
makes sense to have as an option. I don't think however that we should remove the possibility of having a pes stream to provide the pcr.
What does a PCR-only stream consist of? Empty PES packets?
From the tsmux perspective it would be a TS packet with only an adaptation field containing the PCR and no PES header. One of the problem I find while looking at the code is driving when to put a stand alone PCR. The spec says that PCR entries should be found at less than or equal to 1/10 second, in this case the mux should consider any of the program's streams for adding an entry and always use a fixed duration when incrementing its value.
Is this still needed and is somebody going to work on this?
Closing this bug report as no further information has been provided. Please feel free to reopen this bug if you can provide the information asked for. Thanks!