pcm: dmix: fix access to sum-buffer in non-interleaved mixing mode

When dmix uses non-interleaved mixing mode the offset and step width
to sum_buffer was calculated by using the dmix channels instead of
the slave channels. This leads to audio distortions due to frame
corruption.

example:
- With below configuratio, Do aplay on both device in parallel for
audio distortion

pcm.dmix_2_channels {
        type dmix
        ipc_key 5678293
        ipc_perm 0660
        ipc_gid audio
        bindings [0 1]

        slave {
                pcm "hardware"
                channels 2
                periods  4
                period_time 40000
        }
}

pcm.dmix_1_channels {
        type dmix
        ipc_key 5678293
        ipc_perm 0660
        ipc_gid audio
        bindings [0]

        slave {
                pcm "hardware"
                channels 1
                periods  4
                period_time 40000
        }
}

pcm.hardware {
        type hw
        card 0
        channels 2
        rate 48000
        format S16_LE
}

Signed-off-by: Vijay Palaniswamy <vijay.palaniswamy@in.bosch.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
index e9343b19a536e91f5276c1cc0bee6776d8d2e755..8bce7aca85f702817fbc4eb001cd16ee0d91efac 100644 (file)
--- a/src/pcm/pcm_dmix.c
+++ b/src/pcm/pcm_dmix.c
@@ -212,10 +212,10 @@ static void mix_areas(snd_pcm_direct_t *dmix,
                do_mix_areas(size,
                             ((unsigned char *)dst_areas[dchn].addr + dst_areas[dchn].first / 8) + dst_ofs * dst_step,
                             ((unsigned char *)src_areas[chn].addr + src_areas[chn].first / 8) + src_ofs * src_step,
-                            dmix->u.dmix.sum_buffer + channels * dst_ofs + chn,
+                            dmix->u.dmix.sum_buffer + dmix->shmptr->s.channels * dst_ofs + dchn,
                             dst_step,
                             src_step,
-                            channels * sizeof(signed int));
+                            dmix->shmptr->s.channels * sizeof(signed int));
        }
 }
 
@@ -280,10 +280,10 @@ static void remix_areas(snd_pcm_direct_t *dmix,
                do_remix_areas(size,
                               ((unsigned char *)dst_areas[dchn].addr + dst_areas[dchn].first / 8) + dst_ofs * dst_step,
                               ((unsigned char *)src_areas[chn].addr + src_areas[chn].first / 8) + src_ofs * src_step,
-                              dmix->u.dmix.sum_buffer + channels * dst_ofs + chn,
+                              dmix->u.dmix.sum_buffer + dmix->shmptr->s.channels * dst_ofs + dchn,
                               dst_step,
                               src_step,
-                              channels * sizeof(signed int));
+                              dmix->shmptr->s.channels * sizeof(signed int));
        }
 }