[mythtv] [mythtv-commits] Ticket #1104: multichannelaudio support
Paul Catchpole
paul at paulcatchpole.co.uk
Sun Jan 6 23:11:50 UTC 2008
Paul Catchpole wrote:
> Mark Spieth wrote:
>
>>> But, I'm seeing the same clipping/conversion-clicking issue that I saw
>>> in TV, in mythmusic. TV is still fine. It's the centre channel only
>>> again, and seems to happen on any album I pick.
>>>
>>> Any ideas?
>>>
>>>
>> does the same clipping happen in 2ch mode?
>> I had an issue with mad (mp3) in that the audio was distorted (clipped) but
>> no clicking.
>> I think it got introduced with the latest upgrade of libmad but not sure.
>> I saw it in the stereo wave visualization where the waves went all the way
>> peak to peak with rounding of the peaks which provided the clue.
>>
>> my fix was the following. note it shouldnt be happening but this is where
>> the clipping occurs.
>>
>> mark
>>
>> --- maddecoder.cpp (revision 15263)
>> +++ maddecoder.cpp (working copy)
>> @@ -448,6 +448,7 @@
>> static inline signed long fix_sample(unsigned int bits, mad_fixed_t sample)
>> {
>> mad_fixed_t quantized, check;
>> + sample >>= 1; // MRS fudge for clipping problem
>> quantized = sample;
>> check = (sample >> MAD_F_FRACBITS) + 1;
>> if (check & ~1) {
>>
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>>
>>
> Sorry about the delay in testing this, Mark, been a busy week back at work!
>
> It works fine with the audio device for the frontend changed to a
> 2-channel one. It's only when using the real 6-channel device and hence
> the upmixer where the clipping occurs.
>
> Is there anything I can do to narrow this down further?
>
> PC
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>
Also, as an aside, setting the frontend to the 2-channel device on this
patch-40 frontend caused very, very quiet sound in Live TV and
Recordings - although it might have been caused by something odd with my
setup here. The sound I could here sounded rather odd and distorted too.
PC
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