[mythtv] NuppelVideo(Recorder/Player)

Craig Longman craigl at begeek.com
Sun May 18 16:54:29 EDT 2003

Isaac Richards wrote:

>>>Hmm.. Well, the audio you're getting from the card should be 48000 MP2. 
>>>Not sure why it dies but when you resample it to 48kHz, but the pitch
>>>shifting is probably because it's just taking the data as 32kHz instead
>>>of the 48kHz that it is..  Needs to do some resampling in the transcoder
>>>loop to handle that.
>>k, then maybe i do know whats going on.  i had the default profile set
>>up to record (supposedly) mp3 at 32K.  if those settings were being
>>ignored (cause the card encoded it itself) but those parameters were
>>somehow written out anyway, then the re-encode would be trying to read
>>the file in as a 32K MP3, not a 48K MP2 (which would also perhaps
>>account for the annoying whine and hiss that i heard).  any quick
>>pointers on where i should look to see what gets written out?
>It completely ignores the audio settings for the hardware encoding for now.  
>It's recorded at a 48kHz, it's in the file as 48kHz, it gets played back at 
>48kHz.  The transcoding process, however, doesn't pay any attention to that 
>whatsoever, and just assumes that it's at 32kHz because you said it was.  It 
>needs to resample the audio down to 32kHz.
>The annoying whine, on the other hand, is an ivtv driver bug (in the msp3400) 
actually, its not in my case (at least, i'm pretty sure), and this might 
be that problem other ivtv users are seeing.  when i watch the 'raw' 
(mjpeg + mp2) version, it's fine.  there is no whine at all.  when i use 
transcode to _convert_ it to mpeg-4 + mp3, i get the whine.  maybe the 
problem is in the mp3 libs, not ivtv at all?  if a particular version of 
the mp3 libs is incorrectly identifying the stream as an mp3 instead of 
mp2, couldn't that cause all sorts of strange things?  during 
transcoding at least, i'm pretty sure the hardware isn't used at all, right?

i don't know much about all this layer 1/2/3 stuff, so if this all 
sounds like crap, then please forgive me.  i'm adding some debugging to 
my copy of lame to see exactly what its doing (i'm using 3.93.1 iirc) 
and will post more info depending on what i find out.



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