[mythtv] [mythtv-commits] Ticket #1104: multichannelaudio support
Paul Catchpole
paul at paulcatchpole.co.uk
Sun Jan 6 16:14:31 UTC 2008
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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