2010/6/24 David Henningsson <launchpad.web@xxxxxxxxxxxxxx> > These two patches are being used in Ubuntu Lucid (released this April) > and are working well enough to have people asking us to backport them to > Karmic. Today I got an email, asking for the upstream status of one of > these patches, since he wanted them in Fedora. If posting them here > isn't the correct way to upstream them, please tell me so. > > The first one (Fix invalid buffer pointer return value) fixes broken logic: > > This patch improves recovering from underruns, and prevents hangs inside > snd_pcm_write* and snd_pcm_read* due to snd_pcm_avail* returning too > low values. It especially helps low latency situations. > > The second one (Do not report underruns to the ALSA layer) is more a > change of behavior, which could be questioned. The arguments for > removing that code are these: > > * If pulseaudio gets an underrun, the normal way to end that underrun > is to feed it with more buffers. This is different from the ALSA way of > dealing with underruns, which requires hardware buffer pointers to be > reset. > * In addition, underrun signals are delivered asynchronously from > pulseaudio. This means that there might be more buffers on the way to > pulseaudio when the underrun is reported, making the underrun obsolete. > Unfortunately, there is currently no known way to determine whether this > is the case or not. > > // David > > For your test case (mpg123 produces skippy output in 9.10 https://bugs.launchpad.net/ubuntu/+source/alsa-plugins/+bug/464008 play silence when there is underrun http://www.mpg123.de/cgi-bin/viewvc.cgi/trunk/src/output/alsa.c?r1=377&r2=385 static void flush_alsa(audio_output_t *ao) { snd_pcm_t *pcm=(snd_pcm_t*)ao->userptr; /* is this the optimal solution? - we should figure out what we really whant from this function */ debug("alsa drop"); snd_pcm_drop(pcm); debug("alsa prepare"); snd_pcm_prepare(pcm); debug("alsa flush done"); } it implement pause by create an underrun [libmpg123.c:1083] debug: tell: 2207/1 first 0 buffer 0; frame_outs=2542464 [libmpg123.c:623] debug: read of frame 2207 returned 1 (to_decode=1) at sample 2541935 [libmpg123.c:904] debug: got next frame, 1 [libmpg123.c:885] debug: decoding [term.c:158] debug: control for frame: 2207 [alsa.c:246] debug: alsa drop [alsa.c:248] debug: alsa prepare [alsa.c:250] debug: alsa flush done Stopped [alsa.c:246] debug: alsa drop [alsa.c:248] debug: alsa prepare [alsa.c:250] debug: alsa flush done [mpg123.c:632] debug: play_frame [libmpg123.c:620] debug: read frame [parse.c:456] debug: trying to get frame 2208 at 923915 [parse.c:772] debug: Frame 2208 fffb9260 414, next filepos=924333 [index.c:85] debug: wanting to add to fill 552, step 4, size 1000 _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
