I've get M-Audio Revolution 7.1 card some days ago. There still some problems that I can not solve. May be someone can help me? > The Revo has excellent output quality on all channels and is much > better supported by ALSA than any of the Creative Rubbish in Linux > (IMHO). Card doesn't have hardware mixer at all. If you want that some programs be able to play sound simultaneously - you need to setup software mixing. I've managed ALSA dmix plugin to work, but there are some problems. 1) Sound source may have different sample rate, mixer need to convert to one common. I've studied the source of ALSA sample rate convertor in src/pcm/pcm_rate.c - it is awful! It just using linear interpolation - the worst sample rate conversion that can ever be! It make great distortion of a sound. To estimate it imagine, for example, sine wave of 12 kHz, sampled at 48 kHz. It will contains samples 0, 1, 0, -1, 0, 1, etc. If you will convert it to sample rate 96 kHz or 192 kHz you will have triangle wave instead of sine. If you drop all high frequencies that are added with such conversion, the distortion will be approximate (1+cos(wave_freq/sample_rate)/2, which will be about 15% for 12 kHz waves :( It is not possible to have all sound in one sample rate. For example, CD music usually are in 44,1 kHz format and movies are usually are in 48 kHz. All good quality of Revo's Envy24HT chip + AKM DAC will be bringed to nothing by this dull sample rate conversion algorithm. I think it is better to use simple Creative sound card which is able to mix different sample rates at hardware. 2) I still cannot get MPlayer to work through dmixer. It writes me "Cannot set periodsize" error. I've looked through sources, added some debug - it tries to set 1024 period size and fails. I don't know why, may be ALSA guru can help. This issue was already disscussed on ALSA mailing list, there was fix changing *_set to *_set_near. I've tried it. Now MPlayers runs, but plays sound but don't play video. It is surely problem with ALSA because it plays fine with ALSA output to another sound card installed in my computer. 3) Is it possible to write something in asoundrc and get virtual 'Master' mixer that can be able to control all DAC* output channels? I want to change left and right channels volume in MPlayer or XMMS with a single slider. With best regards, Alexander.
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