[Mplayer-users] mp3 downsampling/mixing? (again)

[Christoph Lampert]

>Hi,
>
>> A while ago, I asked about a feature of
>> 
>> 1) changing samplingrate of MP3 streams (e.g from 44100 to 22050 kHz, only
>> supported and easy ratios, like 1/2 or so) at play
>> 
>> 2) downmixing to mono (or playing only single channel in joint-stereo)
>
>yes, i did it... 
>in mp3lib/sr1.c change:
>    fr.down_sample=0; //2;
>to value of 1 (1:2) or 2 (1:4) downsampling of freq.
>
>for getting mono output, change the last parameter of MP3_Decode()
>in dec_audio.c from -1 to 1 (left only) or 2(right only) or 3 (mixed)

Thanks, I tried and it works. For "lowest" setting (1:4 and mixed) I got a 
speedup of 30% for the audio parts (well, that's not much in total, but 
I'm happy about ever percent).

Why is audio decoding faster with -hardframedrop? Audio is not skiped, is it?

gruel

*************

With my brand new K6-2/300 at 301 a short test (-benchmark -vo null) gave

- with framesdrop (not very useful with -vo null, but it RTFMs we otherwise) -

Full MP3 80kbps:
BENCHMARKs: V:  27.369s VO:   0.002s A:   2.341s Sys:   3.787s =   33.498s
BENCHMARK%: V: 81.7017% VO:  0.0074% A:  6.9871% Sys: 11.3038% = 100.0000%

downsampled:
BENCHMARKs: V:  27.210s VO:   0.003s A:   1.648s Sys:   4.784s =   33.646s
BENCHMARK%: V: 80.8731% VO:  0.0094% A:  4.8988% Sys: 14.2186% = 100.0000%

-------------- with hardframedrop --------------------------------------------

Full MP3 80kbps:
BENCHMARKs: V:  25.736s VO:   0.008s A:   2.107s Sys:   5.510s =   33.360s
BENCHMARK%: V: 77.1456% VO:  0.0235% A:  6.3152% Sys: 16.5157% = 100.0000%

downsampled:
BENCHMARKs: V:  25.852s VO:   0.014s A:   1.501s Sys:   5.963s =   33.330s
BENCHMARK%: V: 77.5638% VO:  0.0410% A:  4.5040% Sys: 17.8912% = 100.0000%


-- 
Dipl. math. Christoph Lampert (complex analysis, integral formulae)
Email: gruel at gmx.de                |     Email: lampert at math.chalmers.se


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