[MPlayer-dev-eng] (no subject)

[Nico Sabbi]

On Wednesday 21 May 2008 12:44:52 Todd Huang wrote:
> Hi:
>
>     I am trying to use the mplayer to stream out the encoded data
> (H.264 video + MPEG-4 AAC audio muxed in TS foramt) captured from
> the TV tuner card plugged in the PC over the network.
>
>     By analyzing the PCR value in the PES packets, I found that it
> was the same as the PTS. By checking the source code of mpegtsenc.c
> in the folder of libavformat, I found its value was fixed to be
> equal to the value of PTS.

uhm, are you talking of the demuxer? It would be a very gross
mistake that isn't likely to be present in libavformat.
Evidence the source code, please

>
>     According to the equations of 2-1 in ISO13818-1,
>
>     PCR(i) = PCR_base(i) * 300 + PCR_ext(i)
>
>
>     Can anyone tell me where can I find the source code that
> correctly implements the PCR setting?
>
>     By the way, is the PCR value essential to the software player?
> I know the hardware player uses the PCR to recover the timing of
> the encoder. How is the PCR used by the software player? 

certain software and STB players don't use it at all, but
there are situations where using would give a good hint
to the player and prevent stuttering

> I also 
> noticed that the mplayer utility could play image smoothly even if
> there was no PCR value. However, VLC failed to play image if there
> was no PCR value. Could anyone know the reason?


mplayer tries its best to play the content at all cost, while vlc
is modelled around the reference decoder model

>
>     Is there any relation between the PCR value and the PTS/DTS
> value? I couldn't find any statement in ISO13818-1 mentioning their
> relationship (please correct me if I am wrong). However, VLC fails
> to play the image if the difference between the PCR and the PTS is
> bigger than some limitation.
>

the distance between pcr and dts can't be so big as to lead to 
the violation of buffering constraints imposed by the standard
used as reference (e.g. 230 KB for video and 4KB for audio).

P.S. a title wouldn't hurt, really