alsa_write: Avoid EAGAIN.

Before writing to the sound device, use snd_pcm_avail_update() to
check how many frames alsa will accept and write only that many
frames.

diff --git a/alsa_write.c b/alsa_write.c
index f01b8cf36763ab3ccae6e0e9d5d5c638ce3225d6..cf0f335bebc7426c9b24aad7537601be3dbb0dd7 100644 (file)
--- a/alsa_write.c
+++ b/alsa_write.c
@@ -166,19 +166,19 @@ static int alsa_write_post_select(__a_unused struct sched *s,
 {
        struct private_alsa_write_data *pad = wn->private_data;
        struct writer_node_group *wng = wn->wng;
-       size_t frames, bytes = *wng->loaded - wn->written;
+       size_t bytes = *wng->loaded - wn->written;
        unsigned char *data = (unsigned char*)*wng->bufp + wn->written;
        struct timeval tv;
-       snd_pcm_sframes_t ret;
+       snd_pcm_sframes_t ret, frames, avail;
 
        if (*wng->input_error < 0 && (!pad->handle || bytes < pad->bytes_per_frame)) {
                wn->written = *wng->loaded;
                return *wng->input_error;
        }
        if (!bytes) /* no data available */
-               goto out;
+               return 0;
        if (tv_diff(now, &pad->next_chunk, NULL) < 0)
-               goto out;
+               return 0;
        if (!pad->handle) {
                int err = alsa_init(pad, wn->conf);
                if (err < 0)
@@ -186,30 +186,29 @@ static int alsa_write_post_select(__a_unused struct sched *s,
        }
        frames = bytes / pad->bytes_per_frame;
        if (!frames) /* less than a single frame available */
-               goto out;
+               return 0;
+       avail = snd_pcm_avail_update(pad->handle);
+       if (avail <= 0)
+               goto delay;
+       frames = PARA_MIN(frames, avail);
        ret = snd_pcm_writei(pad->handle, data, frames);
-       if (ret == -EPIPE) {
-               PARA_WARNING_LOG("EPIPE\n");
-               snd_pcm_prepare(pad->handle);
-               return 1;
-       }
-       if (ret < 0 && ret != -EAGAIN) {
-               PARA_WARNING_LOG("alsa error (%zu frames, ret = %d\n",
-                       frames, (int)ret);
+       if (ret < 0) {
+               PARA_WARNING_LOG("%s\n", snd_strerror(-ret));
+               if (ret == -EPIPE) {
+                       snd_pcm_prepare(pad->handle);
+                       return 0;
+               }
+               if (ret == -EAGAIN)
+                       goto delay;
                return -E_ALSA_WRITE;
        }
-       if (ret == -EAGAIN)
-               PARA_DEBUG_LOG("EAGAIN\n");
-       else
-               wn->written += ret * pad->bytes_per_frame;
-       if (ret == frames) /* we wrote everything, try again immediately */
-               pad->next_chunk = *now;
-       else { /* wait until 50% buffer space is available */
-               ms2tv(pad->buffer_time / 2000, &tv);
-               tv_add(now, &tv, &pad->next_chunk);
-       }
-out:
+       wn->written += ret * pad->bytes_per_frame;
        return 1;
+delay:
+       /* wait until 50% buffer space is available */
+       ms2tv(pad->buffer_time / 2000, &tv);
+       tv_add(now, &tv, &pad->next_chunk);
+       return 0;
 }
 
 static void alsa_close(struct writer_node *wn)