From mboxrd@z Thu Jan 1 00:00:00 1970 From: sutar.mounesh@gmail.com Subject: [PATCH 2/2] pcm:plugin: Fix sound capture via MMAP access Date: Tue, 4 Apr 2017 12:00:18 +0530 Message-ID: <1491287418-11297-1-git-send-email-sutar.mounesh@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: patch@alsa-project.org Cc: Mounesh Sutar , Timo Wischer , alsa-devel@alsa-project.org, mounesh_sutar@mentor.com List-Id: alsa-devel@alsa-project.org From: Timo Wischer Distorted sound is heard if the capture device of an ioplug plugin is used, which is accessed through any ALSA plugin (like copy, linear, ...) via MMAP access. E.g. aplay -> loop -> copy -> arecord -M -> aplay -> hw:0 As mentioned in the ALSA API (see pcm/pcm.c:942): The function #snd_pcm_avail_update() have to be called before any mmap begin+commit operation. Signed-off-by: Timo Wischer Signed-off-by: Mounesh Sutar diff --git a/src/pcm/pcm_plugin.c b/src/pcm/pcm_plugin.c index aaea2ab..ec57f6e 100644 --- a/src/pcm/pcm_plugin.c +++ b/src/pcm/pcm_plugin.c @@ -490,7 +490,14 @@ static snd_pcm_sframes_t snd_pcm_plugin_avail_update(snd_pcm_t *pcm) snd_pcm_uframes_t slave_offset; snd_pcm_uframes_t slave_frames = ULONG_MAX; snd_pcm_sframes_t result; - + /* As mentioned in the ALSA API (see pcm/pcm.c:942): + * The function #snd_pcm_avail_update() + * have to be called before any mmap begin+commit operation. + * Otherwise the snd_pcm_areas_copy will not called a second time. + * But this is needed, if the ring buffer wrap is reached and + * there is more data available. + */ + slave_size = snd_pcm_avail_update(slave); result = snd_pcm_mmap_begin(slave, &slave_areas, &slave_offset, &slave_frames); if (result < 0) { err = result; -- 2.7.4