Hi,I am running into a bug with mmap_emulation=true and the plug layer, I had also run into the bug with 1.0.9b.
The symptom of the bug is that the first period (first 2 ?) get repeated on playback.
To reproduce the bug -Modify the the intel-snd8x0 driver so that MMAP is disabled and only the 48Khz sample rate is supported in hardware.
Compile the driver and install it. The changes are attached with this email and reproduced below. 1097c1097 < .info = ( SNDRV_PCM_INFO_INTERLEAVED | ---
.info = (SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_INTERLEAVED |
1099c1099,1100 < SNDRV_PCM_INFO_PAUSE | ---
SNDRV_PCM_INFO_MMAP_VALID |
SNDRV_PCM_INFO_PAUSE |
1143,1144c1144 < //runtime->hw.rates = ichdev->pcm->rates; < runtime->hw.rates = SNDRV_PCM_RATE_48000; ---
runtime->hw.rates = ichdev->pcm->rates;
Since MMAP is now disabled enable mmap_emulation=true in /usr/share/alsa/alsa.conf, below is the modification
pcm.plughw {
<SNIPPED>
type plug
slave.pcm {
type hw
card $CARD
device $DEV
subdevice $SUBDEV
mmap_emulation true #modification to get plughw to work if MMAP is not
supported.
} }Now play any non-48Khz wav file and you will hear the first fragment repeating.
aplay -D plughw:0,0 <wav file name>If anyone knows of a workaround or if you need any more info please let me know.
Thanks, Nikhil----- Original Message ----- From: "Takashi Iwai" <tiwai@xxxxxxx>
To: "Nikhil Rao" <nikhil_p_rao@xxxxxxxxxxx> Cc: <alsa-devel@xxxxxxxxxxxxxxxxxxxxx> Sent: Wednesday, April 12, 2006 4:10 AM Subject: Re: Fw: Bug with PCM plug layer with mmap emulation=true ?
At Mon, 10 Apr 2006 15:51:14 -0700, Nikhil Rao wrote:Hi Takashi,I havent received any response to the query below, let me know if I need toadd more information.Sorry I seem to have missed that post.thanks, Nikhil----- Original Message ----- From: "Nikhil Rao" <nikhil_p_rao@xxxxxxxxxxx>To: <alsa-devel@xxxxxxxxxxxxxxxxxxxxx> Sent: Monday, April 03, 2006 4:26 PM Subject: Bug with PCM plug layer with mmap emulation=true ? > Hello, >> I have observed that the using pcm plug layer with mmap emulation=true > in > alsa.conf, causes the first period of data to be sent twice to the > driver.> I also verified this by dumping the PCM data to a file (using the copy > callback)This could be a bug. The mmap_emulation mode wasn't debugged for long time.> I have tried experiments using the ALSA driver (ver 1.0.10) written by > me> for my development system (an SoC) > and also the intelx80 driver on a Suse 10.0 system (ALSA ver 1.0.9b). I> modified the intelx80 driver so that it only supports 48Khz and then > used > the plughw device to playout a 44Khz sample. There is a distinct > stutter> audible at the beginning of the clip caused by the first period being > presented twice to the hardware. >> Is this a known problem ? if so, is a workaround available (my > development> platform does not support mmap currently).Well, another question is whether really mmap is necessary for your device. Any particular applications require the mmap access exclusively? Anyway, the bug should be fixed. First, could you try the latest ALSA (1.0.11rc5 was released yesterday)? Debugging old codes is a waste of time. The symptom sounds like a problem with rate plugin. The rate plugin defers the transfer until a whole period size is filled. So, if the problem still exists, please describe the method you checked this behavior in details, too. Takashi
Attachment:
intel8x0.diff
Description: Binary data
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