[Vorbis] RE: Re: very low bandwidth encoding

[Andy Baxter]

On Thu, 23 Sep 2004 10:38:21 +0200, Giuliano Pochini wrote:

> 
> On 22-Sep-2004 Andy Baxter wrote:
> 
>> is giving fairly decent sound at 12 kbps mono if I play it through ogg123,
>> but sounds tinny and strange if I play through alsaplayer. xmms has the
>> same problem. zinf plays these files OK - same as ogg123.
> 
> ALSA uses a rough and fast "pick the nearest sample" resampling
> algorithm, which gives very bad results. Alsaplayer uses a fixed
> sample rate (you can change it via command line). 

When it plays wavs, it seems to forget about the sample rate in the header
altogether and just play at 44100 Hz whatever, so the 11025 Hz wavs I've
written come out at 4 times the original speed. But it doesn't do this for
ogg files - it plays at the right speed, but with a strange tinny sound
which you don't get with ogg123. Like it's playing inside a biscuit tin,
plus a weird sweeping effect in the high pitches. The same effect happens
with the other linux players I mentioned - kaboodle and noatun, so I guess
it's caused by the same problem.

> Xmms tries to
> match the file's sample rate but, if the card can't do it, ALSA
> does the resampling. IIRC alsa-1.0.7 will use linear interpolation.

I just found out that xmms plays OK through the disk writer output plugin,
so it's probably more to do with its internal resampling routines than
the ogg input plugin.