[mythtv] [mythtv-commits] Ticket #5900: AO: Generalise upmix and AC-3 encoding

Paul Gardiner lists at glidos.net
Thu Nov 13 11:02:04 UTC 2008

foo bar wrote:
> 2008/11/13 John P Poet <jppoet at gmail.com>:
>> So, you are saying that if I do:
>> aplay -D iec958 music.wav
>> where music.wav is encoded at 44.1KHz, that alsa will convert that to
>> 48KHz, then back to 44.1KHz before sending it to my receiver, just so
>> it can "mix"?  That is ugly.  Guess I will have to craft up a
>> asound.conf file to tell it not to do that.   Been a while since I
>> have had to do that -- gonna need a refresher.
>> My receiver definitely says it is receiving a 44.1KHz signal, so I
>> know the sound card is delivering it at the correct rate.
> No. I assume iec958 is a straight hw device and that ALSA doesn't do
> sw mixing and therefore doesn't resample in that case.
> It would resample if you were to do aplay music.wav or aplay -D
> default music.wav or aplay -D plughw:x,y music.wav, which is why
> resampling in myth is best thing for the majority.
> Have you actually tried the SRC in myth?

I don't know if this is relevant, but I use a .asoundrc file in the
mythtv user's home directory, containing:

pcm.!default {
type plug
slave {
pcm "spdif"
rate 48000
format S16_LE

That makes mythtv and mplayer output to spdif, with non 48000 content
resampled to 4800.


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