Teach writers to abort gracefully on early EOF.
authorAndre Noll <maan@tuebingen.mpg.de>
Sun, 5 Sep 2021 18:16:59 +0000 (20:16 +0200)
committerAndre Noll <maan@tuebingen.mpg.de>
Thu, 21 Oct 2021 17:53:06 +0000 (19:53 +0200)
For very short streams it may happen that the receiver and decoder
unregister themselves from the buffer tree before the writer had a
chance to query the information from the decoder which it needs to
open the audio device. This leads to errors such as

Aug 25 14:24:51 schubert (5) get_btr_value: cmd sample_rate: Operation not supported
Aug 25 14:24:51 schubert (5) get_btr_value: cmd channels: Operation not supported
Aug 25 14:24:51 schubert (5) get_btr_value: cmd sample_format: Operation not supported
Aug 25 14:24:51 schubert (4) alsa_init: channels count not available: Invalid argument

This may happen with all receivers, audio formats and writers,
although it is most common with ogg streams.

This commit changes get_btr_sample_rate() and friends to return a
standard error code rather than assuming success. The alsa, ao and
oss writers are patched to check the return value and fail gracefully
if one of these functions fails.

alsa_write.c
ao_write.c
oss_write.c
write.h
write_common.c

index 9822da6..2d83402 100644 (file)
@@ -297,13 +297,18 @@ again:
                if (bytes == 0) /* no data available */
                        return 0;
                pad = wn->private_data = para_calloc(sizeof(*pad));
-               get_btr_sample_rate(btrn, &val);
+               ret = get_btr_sample_rate(btrn, &val);
+               if (ret < 0)
+                       goto err;
                pad->sample_rate = val;
-               get_btr_channels(btrn, &val);
+               ret = get_btr_channels(btrn, &val);
+               if (ret < 0)
+                       goto err;
                pad->channels = val;
-               get_btr_sample_format(btrn, &val);
+               ret = get_btr_sample_format(btrn, &val);
+               if (ret < 0)
+                       goto err;
                pad->sample_format = get_alsa_pcm_format(val);
-
                PARA_INFO_LOG("%u channel(s), %uHz\n", pad->channels,
                        pad->sample_rate);
                ret = alsa_init(wn);
index 447dea8..037b929 100644 (file)
@@ -357,9 +357,15 @@ static int aow_post_select(__a_unused struct sched *s, void *context)
                        goto remove_btrn;
                if (ret == 0)
                        return 0;
-               get_btr_sample_rate(wn->btrn, &rate);
-               get_btr_channels(wn->btrn, &ch);
-               get_btr_sample_format(wn->btrn, &format);
+               ret = get_btr_sample_rate(wn->btrn, &rate);
+               if (ret < 0)
+                       goto remove_btrn;
+               ret = get_btr_channels(wn->btrn, &ch);
+               if (ret < 0)
+                       goto remove_btrn;
+               ret = get_btr_sample_format(wn->btrn, &format);
+               if (ret < 0)
+                       goto remove_btrn;
                ret = aow_init(wn, rate, ch, format);
                if (ret < 0)
                        goto remove_btrn;
index 311a514..0565167 100644 (file)
@@ -199,9 +199,15 @@ static int oss_post_select(__a_unused struct sched *s, void *context)
 
                if (sound_device_is_busy())
                        return 0;
-               get_btr_sample_rate(btrn, &rate);
-               get_btr_channels(btrn, &ch);
-               get_btr_sample_format(btrn, &format);
+               ret = get_btr_sample_rate(btrn, &rate);
+               if (ret < 0)
+                       goto out;
+               ret = get_btr_channels(btrn, &ch);
+               if (ret < 0)
+                       goto out;
+               ret = get_btr_sample_format(btrn, &format);
+               if (ret < 0)
+                       goto out;
                ret = oss_init(wn, rate, ch, format);
                if (ret < 0)
                        goto out;
diff --git a/write.h b/write.h
index cb0beff..833cb69 100644 (file)
--- a/write.h
+++ b/write.h
@@ -66,7 +66,7 @@ const struct writer *writer_get(int wid);
 const char *writer_name(int wid);
 void register_writer_node(struct writer_node *wn, struct btr_node *parent,
                struct sched *s);
-void get_btr_sample_rate(struct btr_node *btrn, int32_t *result);
-void get_btr_channels(struct btr_node *btrn, int32_t *result);
-void get_btr_sample_format(struct btr_node *btrn, int32_t *result);
+int get_btr_sample_rate(struct btr_node *btrn, int32_t *result);
+int get_btr_channels(struct btr_node *btrn, int32_t *result);
+int get_btr_sample_format(struct btr_node *btrn, int32_t *result);
 void print_writer_helps(bool detailed);
index 14cc98a..41c3eb2 100644 (file)
@@ -174,24 +174,24 @@ void print_writer_helps(bool detailed)
        }
 }
 
-static void get_btr_value(struct btr_node *btrn, const char *cmd,
+static int get_btr_value(struct btr_node *btrn, const char *cmd,
                int32_t *result)
 {
        char *buf = NULL;
        int ret = btr_exec_up(btrn, cmd, &buf);
 
-       if (ret < 0) {
-               /*
-                * This really should not happen. It means one of our parent
-                * nodes died unexpectedly. Proceed with fingers crossed.
-                */
-               PARA_CRIT_LOG("cmd %s: %s\n", cmd, para_strerror(-ret));
-               *result = 0;
-               return;
-       }
+       *result = 0;
+       /*
+        * Errors may happen when the decoder returns EOF before the writer had
+        * a chance to query the buffer tree for the channel count, sample rate
+        * etc.
+        */
+       if (ret < 0)
+               return ret;
        ret = para_atoi32(buf, result);
        assert(ret >= 0);
        free(buf);
+       return ret;
 }
 
 /**
@@ -200,11 +200,11 @@ static void get_btr_value(struct btr_node *btrn, const char *cmd,
  * \param btrn Where to start the search.
  * \param result Filled in by this function.
  *
- * This function is assumed to succeed and terminates on errors.
+ * \return Standard.
  */
-void get_btr_sample_rate(struct btr_node *btrn, int32_t *result)
+int get_btr_sample_rate(struct btr_node *btrn, int32_t *result)
 {
-       get_btr_value(btrn, "sample_rate", result);
+       return get_btr_value(btrn, "sample_rate", result);
 }
 
 /**
@@ -212,10 +212,12 @@ void get_btr_sample_rate(struct btr_node *btrn, int32_t *result)
  *
  * \param btrn See \ref get_btr_sample_rate.
  * \param result See \ref get_btr_sample_rate.
+ *
+ * \return Standard.
  */
-void get_btr_channels(struct btr_node *btrn, int32_t *result)
+int get_btr_channels(struct btr_node *btrn, int32_t *result)
 {
-       get_btr_value(btrn, "channels", result);
+       return get_btr_value(btrn, "channels", result);
 }
 
 /**
@@ -223,8 +225,10 @@ void get_btr_channels(struct btr_node *btrn, int32_t *result)
  *
  * \param btrn See \ref get_btr_sample_rate.
  * \param result Contains the sample format as an enum sample_format type.
+ *
+ * \return Standard.
  */
-void get_btr_sample_format(struct btr_node *btrn, int32_t *result)
+int get_btr_sample_format(struct btr_node *btrn, int32_t *result)
 {
-       get_btr_value(btrn, "sample_format", result);
+       return get_btr_value(btrn, "sample_format", result);
 }