On Tue, 28 Oct 2003, Jaroslav Kysela wrote:
> On Tue, 28 Oct 2003, Takashi Iwai wrote:
>
> > At Mon, 27 Oct 2003 13:11:58 +0100,
> > Andreas Mohr wrote:
> > >
> > > Hello Takashi,
> > >
> > > On Mon, Oct 27, 2003 at 01:01:37PM +0100, Takashi Iwai wrote:
> > > > At Sat, 25 Oct 2003 22:02:21 +0200,
> > > > Andreas Mohr wrote:
> > > > > Or, as a short summary:
> > > > > The application is perfectly well aware of how many bytes there are left
> > > > > to read (from calling SNDCTL_DSP_GETISPACE) and then does a read() with
> > > > > this amount of bytes, however since the ALSA OSS layer attempts to read
> > > > > this byte amount in blocks of runtime->oss.period_bytes bytes from the sound
> > > > > device, we ARTIFICIALLY cause a -EAGAIN to be returned due to insufficient
> > > > > available data, thus potentially confusing many OSS applications.
> > > > >
> > > > > Now what to do here?
> > > >
> > > > this problem is a bit touch, because the ALSA OSS layer does the
> > > > sample-rate conversion, etc.
> > > > when the sample rate is converted between 44.1kHz and 48kHz, some
> > > > round error may happen and it will be accumulated. hence, the size
> > > > will be different between two cases: reading a whole period once and
> > > > reading a period by multiple calls.
> > > >
> > > > i'll take a more deeper look...
> > > Ah, thanks! (also for the explanation given above)
> > >
> > > Given that 1.0 is approaching, it'd certainly be useful to get such a
> > > problem fixed ;-)
> >
> > i come to believe that it's a bug, too.
> > as you wrote, the fix is easy except for the rare problem what i
> > mentioned above. in that case (e.g. the sample-rate conversion
> > between 44.1 and 48khz required), you'll still get -EAGAIN
> > occasionally. but normally, it seems ok.
> >
> > the attached is the patch to fix the original problem.
> > to take back to the old behavior (always reading a whole period),
> > you can write "whole-frag" command to the proc file.
> >
> > anyway, i'll try a bit more to solve the problem above.
>
> I think that the problem is at another place. I'm investigating the bug in
> code now.
Yes, several assumptions were made and the SPACE ioctls were a bit broken.
I've put a fix to our CVS (also included to this e-mail). Hopefully, it
won't break another OSS applications.
Jaroslav
Index: pcm_oss.c
===================================================================
RCS file: /cvsroot/alsa/alsa-kernel/core/oss/pcm_oss.c,v
retrieving revision 1.53
diff -u -r1.53 pcm_oss.c
--- pcm_oss.c 30 Sep 2003 09:28:26 -0000 1.53
+++ pcm_oss.c 28 Oct 2003 13:26:12 -0000
@@ -125,8 +125,8 @@
if (runtime->period_size == runtime->oss.period_bytes)
return frames;
if (runtime->period_size < runtime->oss.period_bytes)
- return frames * (runtime->oss.period_bytes / runtime->period_size);
- return frames / (runtime->period_size / runtime->oss.period_bytes);
+ return (frames * runtime->period_size) / runtime->oss.period_bytes;
+ return (frames * runtime->oss.period_bytes) / runtime->period_size;
}
static int snd_pcm_oss_format_from(int format)
@@ -451,7 +451,7 @@
sw_params->tstamp_mode = SNDRV_PCM_TSTAMP_NONE;
sw_params->period_step = 1;
sw_params->sleep_min = 0;
- sw_params->avail_min = runtime->period_size;
+ sw_params->avail_min = 1;
sw_params->xfer_align = 1;
if (atomic_read(&runtime->mmap_count) ||
(substream->oss.setup && substream->oss.setup->nosilence)) {
@@ -470,7 +470,6 @@
snd_printd("SW_PARAMS failed: %i\n", err);
goto failure;
}
- runtime->control->avail_min = runtime->period_size;
runtime->oss.periods = params_periods(sparams);
oss_period_size = snd_pcm_plug_client_size(substream,
params_period_size(sparams));
@@ -883,7 +882,7 @@
if (tmp <= 0)
return xfer > 0 ? (snd_pcm_sframes_t)xfer :
tmp;
runtime->oss.bytes += tmp;
- runtime->oss.buffer_used = runtime->oss.period_bytes;
+ runtime->oss.buffer_used = tmp;
}
tmp = bytes;
if ((size_t) tmp > runtime->oss.buffer_used)
@@ -1425,6 +1424,7 @@
snd_pcm_substream_t *substream;
snd_pcm_runtime_t *runtime;
snd_pcm_sframes_t delay;
+ int fixup;
struct count_info info;
int err;
@@ -1447,9 +1447,13 @@
if (err == -EPIPE || err == -ESTRPIPE) {
err = 0;
delay = 0;
+ fixup = 0;
+ } else {
+ fixup = runtime->oss.buffer_used;
}
} else {
err = snd_pcm_oss_capture_position_fixup(substream, &delay);
+ fixup = -runtime->oss.buffer_used;
}
if (err < 0)
return err;
@@ -1469,7 +1473,8 @@
if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
snd_pcm_oss_simulate_fill(substream);
} else {
- info.blocks = delay / runtime->period_size;
+ delay = snd_pcm_oss_bytes(substream, delay) + fixup;
+ info.blocks = delay / runtime->oss.period_bytes;
}
if (copy_to_user(_info, &info, sizeof(info)))
return -EFAULT;
@@ -1481,6 +1486,7 @@
snd_pcm_substream_t *substream;
snd_pcm_runtime_t *runtime;
snd_pcm_sframes_t avail;
+ int fixup;
struct audio_buf_info info;
int err;
@@ -1500,7 +1506,7 @@
if (runtime->oss.prepare) {
if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
info.bytes = runtime->oss.period_bytes * runtime->periods;
- info.fragments = runtime->periods;
+ info.fragments = runtime->oss.periods;
} else {
info.bytes = 0;
info.fragments = 0;
@@ -1511,16 +1517,19 @@
if (err == -EPIPE || err == -ESTRPIPE) {
avail = runtime->buffer_size;
err = 0;
+ fixup = 0;
} else {
avail = runtime->buffer_size - avail;
+ fixup = -runtime->oss.buffer_used;
}
} else {
err = snd_pcm_oss_capture_position_fixup(substream, &avail);
+ fixup = runtime->oss.buffer_used;
}
if (err < 0)
return err;
- info.bytes = snd_pcm_oss_bytes(substream, avail);
- info.fragments = avail / runtime->period_size;
+ info.bytes = snd_pcm_oss_bytes(substream, avail) + fixup;
+ info.fragments = info.bytes / runtime->oss.period_bytes;
}
#ifdef OSS_DEBUG
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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