The following issue has been ASSIGNED. ====================================================================== <https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1151> ====================================================================== Reported By: felix Assigned To: jcdutton ====================================================================== Project: ALSA - driver Issue ID: 1151 Category: PCI - emu10k1 Reproducibility: always Severity: minor Priority: normal Status: assigned Distribution: Suse 9.1 Kernel Version: 2.6.5-7.147-default ====================================================================== Date Submitted: 06-02-2005 23:07 CEST Last Modified: 07-18-2006 14:45 CEST ====================================================================== Summary: Audigy sampling rate seems off Description: I'm doing an experiment that involves generating a tone, sending it out the sound card and into a (passive) circuit, and recording from the circuit back into line in at the same time. When I play a sample: mono, 8kHz sample rate, containing a synthetic 1kHz sin signal, the recording I get is of a signal 1000.12Hz. If I send 100Hz, I get back 100.012Hz. I use 'snd' to do a 256K-point FFT across a 10 second sample just to be sure. I've also verified this using FFTW and correlation-based programs of my own. I've also verified that the reference 1kHz and 100Hz signals are exact. As a sanity check, I tried the same experiment on the built-in sound card on that same PC. The signals come back correct. Note the seeming coincidence that the frequency of the signal coming back is 1/8000 higher than the signal output. I've never seen anything like it. Not that I've been looking before... ====================================================================== ---------------------------------------------------------------------- sst4 - 06-03-05 00:29 ---------------------------------------------------------------------- If it's rather off by 1/8192 (8192 is 2 to 13th power), then it'd look very much programmatic. Just an observation - I know nothing about "audigy". ---------------------------------------------------------------------- perex - 06-03-05 10:59 ---------------------------------------------------------------------- Note that the routine which calculates "pitch" for playback is in alsa-kernel/pci/emu10k1/emupcm.c - emu10k1_calc_pitch_target(). It's quite simple, so you may do experiments with it. Also, upgrade to latest ALSA 1.0.9, there are some cleanups for the sample cache, and it might be also related. ---------------------------------------------------------------------- felix - 06-03-05 17:45 ---------------------------------------------------------------------- to sst4, re. powers of 2: Good point. I also tried 32kHz sampling, and the problem follows! ie the frequency error drops to ~ 1/32000. I *wish* I could tell whether it was 32k or 32K, but my measurement tools can't give me enough significant digits :-( I can, however, try more sampling rates to see whether the problem follows 1/sample rate or jumps between powers of 2... re. audigy: my vague. /proc/asound/cards says: 0 [Audigy ]: Audigy - Sound Blaster Audigy Sound Blaster Audigy (rev.3, serial:0x531102) at 0xa000, irq 11 to perex: Thanks for the code pointers. Will also definitely upgrade to 1.0.9. ---------------------------------------------------------------------- felix - 06-04-05 03:42 ---------------------------------------------------------------------- More results: Upgraded kernel to 2.6.11.11, installed 1.09a drivers outside the kernel and all 1.09 libraries and tools. The problem remains. However... I ran a spectrum of sampling rates through emu10k1_calc_pitch_target() and found that from 6kHz through 96kHz, at intervals of 3kHz, pitch_target ends up being divisible by 1024. And as it turns out, the frequency of a tone at these sampling rates is exactly correct. Perhaps this will serve as a clue to someone familiar with the driver and hardware. For all I know, this is common to all emu10k1 cards. And yes, 44.1kHz displays the error, whereas 48kHz and 96kHz do not. ---------------------------------------------------------------------- felix - 06-04-05 03:58 ---------------------------------------------------------------------- Two more exciting data, to see whether it is possible to isolate the problem to playback or recording: 1. synthesize and aplay a 1kHz tone at 8kHz sampling rate, simultaneously record at 12kHz sampling rate => Recorded tone is shifted up by ~ 1/8k 2. synthesize and aplay a 1kHz tone at 12kHz sampling rate, simultaneously record at 8kHz sampling rate => recorded tone is EXACTLY 1000Hz Issue History Date Modified Username Field Change ====================================================================== 06-02-05 23:07 felix New Issue 06-02-05 23:07 felix Distribution => Suse 9.1 06-02-05 23:07 felix Kernel Version => 2.6.5-7.147-default 06-03-05 00:29 sst4 Note Added: 0004879 06-03-05 10:59 perex Note Added: 0004883 06-03-05 17:44 felix Note Added: 0004884 06-03-05 17:45 felix Note Edited: 0004884 06-04-05 03:42 felix Note Added: 0004885 06-04-05 03:58 felix Note Added: 0004886 07-18-06 14:45 jcdutton Status new => assigned 07-18-06 14:45 jcdutton Assigned To => jcdutton ====================================================================== ------------------------------------------------------------------------- Take Surveys. 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