[mythtv] Re: Software AC3 decoding when watching TV

[Tj]

Sorry for the late reply.. was trying to figure out how to actually 
record a short clip.

>I think this http://liba52.sourceforge.net/ should be installed so
>ffmpeg can decode ac3.
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I did have that installed - via an RPM for mplayer to play ac3... Myth 
also has libavcodec, does it uses that or uses the liba52.so? It seems 
to use the internal libavcodec...

If I start and stop mythbackend mythfrontend enough times, I actually 
got AC3 sound working!!!

a52_decode_frame in libs/libavcodec/a52dec.c only works when buf_size is 
1024. Anything else there's no sounds..

>Depends. AC3 should be in privete_stream_1 PES packets in TS stream. 
>At least in DVB and American ATSC.  This is where ffmpeg searches for
>it, see mpegps_read_packet and mpegps_read_pes_header. What do you
>mean with "startcode"?
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startcode is some variable used by the mpegps_read_pes_header function 
(line 1359: libs/libavformat/mpeg.c). It's called by
mpegps_read_packet (line 1500: libs/libavformat/mpeg.c). For Australia 
Channel TEN, the AC3 APID has a startcode of 0x1c0, which is then 
assigned the codec_id of CODEC_ID_MP2... (AC3 has a startcode of 0x80)..

Also, since it's a ts stream, shouldn't libs/libavformat/mpegts.c be 
used instead?

>Do you have a bit of stream somewhere? I could take a look.
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you can get it here at http://treblid.dyndns.org/2guys.nuv (approx 
20MB). Pls tell me if it doesn't work.....

If it's any important, the following are my setup for that channel...

VPID:512 (0x200)
APID:651 (0x28b)
Service ID: 1665 (0x681)

It's SDTV with AC3 audio.

Thanks...


Regards.