[mythtv-users] IPTV Recording: No Sound. Audio codec problem?

Pedro Pessoa prp at pobox.com
Wed Jan 24 09:40:43 UTC 2007

Hello Nate, everyone,

I was having a similar problem. Using MythTV, some of my IPTV channels were in 
spanish and not in portuguese as I was getting them from the provider STB. 
Spanish almost like as having no audio! :-)

When using the STB the channel audio was played back in pt, but as soon as I 
switched over to Myth I would get them in es. 
I couldn't figure out what was going on. I didn't event know if the multicast 
stream could cary more than one audio channel. I was thinking that the pt 
audio was on another multicast stream. However, from the ethereal capture, 
when the STB was being used, I could not see any other multicast subscription 
from the STB! Weird!

So, this morning, while getting out of bed, it struck me! Could the MC stream 
be carying more audio channels? Maybe just like a DVD playback when you have 
to select the audio channel and subtitle. Would MythTV support this?
Yes! There it was, on the audio channel selection, another audio channel, the 
pt one! Great!!!

Nate, have you checked the audio channel selection? 
This is so straight forward that I don't know why I didn't remeber to do it 

One question to everyone. How can on channel be configured so that, by 
default, when whatched on live tv, or when the recording from it are played, 
it used one specific audio channel?

Thanks everyone!

On Friday 19 January 2007 02:17, Nate Crosno wrote:
> Hi All,
> Never got any hits on this, but I have found out a little more.  Mplayer
> is able to play the sound from these files, but it's way out of sync
> with the video...better than nothing though.  Here is part of the output
> from mplayer:
> Opening audio decoder: [liba52] AC3 decoding with liba52
> dec_audio: Allocating 3840 bytes for input buffer.
> dec_audio: Allocating 6144 + 65536 = 71680 bytes for output buffer.
> COLLECT_SECTION, start: 64, size: 184, collected: 184
> SKIP: 0+1, TID: 0, TLEN: 13, COLLECTED: 184
> PARSE_PAT: section_len: 13, section 0/0
> PROG: 35 (1-th of 1), PMT: 2
> AC3: 2.0 (stereo)  48000 Hz  192.0 kbit/s
> A52 flags before a52_frame: 0x2A
> A52 flags after a52_frame: 0x2
> AUDIO: 48000 Hz, 2 ch, s16le, 192.0 kbit/12.50% (ratio: 24000->192000)
> Selected audio codec: [a52] afm: liba52 (AC3-liba52)
> Any ideas on how to get it playing in Myth is greatly appreciated!
> Trying not to go through the video screen.
> Thanks,
> Nate
> -----Original Message-----
> From: Nate Crosno
> Sent: Tuesday, January 09, 2007 11:38 AM
> To: 'Discussion about mythtv'
> Subject: IPTV Recording: No Sound. Audio codec problem?
> Hi All, I'm reposting a previous question to the list but breaking out
> the more pressing question at the moment, adding more info, and changing
> the subject line...
> I have been able to view and save the IPTV streams on the Myth box that
> are going to my little Amino STB by splitting the cable with hub.  I can
> save the stream with a command like this:
> vlc udp:@ --ts-dump-file test.mpg
> Or I can view the stream with either of these commands:
> vlc udp:@
> xine udp://
> ...however I do not get any sound.  I copied the test file to a windows
> box and did get sound when watching VLC.  I have tried to compare the
> file with known good files saved off my HD DVB card and cannot tell the
> difference -- both have A/52 set as the audio codec and MPEGTS for video.
> Using "midentify", I get the following when comparing the saved IPTV
> file to a known good HD file:
> Ati HD Wonder File        IPTV File
> ID_DEMUXER=mpegts            ID_DEMUXER=mpegts
> ID_VIDEO_FORMAT=0x10000002    ID_VIDEO_FORMAT=0x10000002
> ID_VIDEO_BITRATE=80000000    ID_VIDEO_BITRATE=15000000
> ID_VIDEO_FPS=59.940        ID_VIDEO_FPS=29.970
> ID_VIDEO_ASPECT=0.0000        ID_VIDEO_ASPECT=0.0000
> ID_AUDIO_BITRATE=384000        ID_AUDIO_BITRATE=192000
> ID_AUDIO_RATE=48000        ID_AUDIO_RATE=48000
> ID_AUDIO_NCH=2            ID_AUDIO_NCH=2
> ID_LENGTH=7.26            ID_LENGTH=2.30
> ID_VIDEO_CODEC=mpegpes        ID_VIDEO_CODEC=mpegpes
> Any ideas on how to get the audio working would be greatly appreciated.
> Also, I tried to play the IPTV file in myth via "mythtv test.mpg", but
> that bombed out. I can provide logs if anyone is interested.
> Once I get the sound playing at all, I'll worry about step 2, which is
> getting Myth to record and play the files.
> Thanks,
> -Nate
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