pcm_a52: Determine virtual hardware pointer upon slave pointer

Calculate the pointer upon the hardware pointer of the slave by
querying its available frames. Thereby we can guarantee that our
transfer routine will accept as many frames as the pointer indicates.

BugLink: https://github.com/alsa-project/alsa-plugins/pull/8
Signed-off-by: Alexander Motzkau <a.motzkau@web.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/a52/pcm_a52.c b/a52/pcm_a52.c
index b005bc2040c0113f69ca081e6f7f75d69616f64c..653de12d7fd2e0a6b725dbdbad116848ef8d79d4 100644 (file)
--- a/a52/pcm_a52.c
+++ b/a52/pcm_a52.c
@@ -325,21 +325,18 @@ static snd_pcm_sframes_t a52_transfer(snd_pcm_ioplug_t *io,
 /*
  * pointer callback
  *
- * Calculate the current position from the delay of slave PCM
+ * Calculate the current position from the available frames of slave PCM
  */
 static snd_pcm_sframes_t a52_pointer(snd_pcm_ioplug_t *io)
 {
        struct a52_ctx *rec = io->private_data;
-       snd_pcm_sframes_t delay;
+       snd_pcm_sframes_t avail;
        snd_pcm_state_t state;
-       int err;
 
        state = snd_pcm_state(rec->slave);
        switch (state) {
        case SND_PCM_STATE_RUNNING:
        case SND_PCM_STATE_DRAINING:
-               if ((err = snd_pcm_delay(rec->slave, &delay)) < 0)
-                       return err;
                break;
        case SND_PCM_STATE_XRUN:
        case SND_PCM_STATE_SUSPENDED:
@@ -348,16 +345,25 @@ static snd_pcm_sframes_t a52_pointer(snd_pcm_ioplug_t *io)
                return 0;
        }
 
-       if (delay < 0 || delay >= (snd_pcm_sframes_t)rec->slave_buffer_size)
-               delay = 0;
-       delay = (snd_pcm_sframes_t)io->appl_ptr - delay;
-       if (delay < 0) {
-               delay += io->buffer_size;
-               if (delay < 0)
-                       delay = 0;
+       avail = 0;
+
+       /* Write what we have from outbuf. */
+       write_out_pending(io, rec);
+
+       /* If there is anything remaining in outbuf, we can't
+        * accept any full packets. */
+       if (rec->remain == 0)
+       {
+               /* Round the slave frames to multiples of the packet size. */
+               avail += (snd_pcm_avail_update(rec->slave) / rec->avctx->frame_size) * rec->avctx->frame_size;
        }
-       delay %= io->buffer_size;
-       return delay;
+
+       if (avail < 0)
+               avail = 0;
+       else if (avail >= io->buffer_size)
+               avail = io->buffer_size - 1;
+
+       return (io->appl_ptr + avail) % io->buffer_size;
 }
 
 /* set up the fixed parameters of slave PCM hw_parmas */