If the virtual sink is moved to a new master right after it has been created,
then the virtual sink input's memblockq can be rewound to a negative read
index. The data written prior to the move starts from index zero, so after the
rewind there's a bit of silence. If the memblockq doesn't have a silence
memchunk set, then pa_memblockq_peek() will return zero in such case, and the
returned memchunk's memblock pointer will be NULL.
That scenario wasn't taken into account in the implementation of
sink_input_pop_cb. Setting a silence memchunk for the memblockq solves this
problem, because pa_memblock_peek() will now return a valid memblock if the
read index happens to point to a hole in the memblockq.
I believe this isn't the best possible solution, though. It doesn't really make
sense to rewind the sink input's memblockq beyond index 0 in the first place,
because now when the stream starts to play to the new master sink, there's some
unnecessary silence before the actual data starts. This is a small problem,
though, and I don't grok the rewinding system well enough to know how to fix
this issue properly.
I went through all files that call pa_memblockq_peek() to see if there are more
similar bugs. play-memblockq.c was the only one that looked to me like it might
be broken in the same way. I didn't try reproducing the bug with
play-memblockq.c, though, so I just added a FIXME comment there.
pa_sink_new_data sink_data;
pa_bool_t use_volume_sharing = FALSE;
pa_bool_t force_flat_volume = FALSE;
pa_sink_new_data sink_data;
pa_bool_t use_volume_sharing = FALSE;
pa_bool_t force_flat_volume = FALSE;
u->sink->input_to_master = u->sink_input;
u->sink->input_to_master = u->sink_input;
- /* (9) IF YOU REQUIRE A FIXED BLOCK SIZE MAKE SURE TO PASS A
- * SILENCE MEMBLOCK AS LAST PARAMETER
- * HERE. pa_sink_input_get_silence() IS USEFUL HERE. */
- u->memblockq = pa_memblockq_new(0, MEMBLOCKQ_MAXLENGTH, 0, pa_frame_size(&ss), 1, 1, 0, NULL);
+ pa_sink_input_get_silence(u->sink_input, &silence);
+ u->memblockq = pa_memblockq_new(0, MEMBLOCKQ_MAXLENGTH, 0, pa_frame_size(&ss), 1, 1, 0, &silence);
+ pa_memblock_unref(silence.memblock);
- /* (10) INITIALIZE ANYTHING ELSE YOU NEED HERE */
+ /* (9) INITIALIZE ANYTHING ELSE YOU NEED HERE */
pa_sink_put(u->sink);
pa_sink_input_put(u->sink_input);
pa_sink_put(u->sink);
pa_sink_input_put(u->sink_input);
} pa_rtp_context;
pa_rtp_context* pa_rtp_context_init_send(pa_rtp_context *c, int fd, uint32_t ssrc, uint8_t payload, size_t frame_size);
} pa_rtp_context;
pa_rtp_context* pa_rtp_context_init_send(pa_rtp_context *c, int fd, uint32_t ssrc, uint8_t payload, size_t frame_size);
+
+/* If the memblockq doesn't have a silence memchunk set, then the caller must
+ * guarantee that the current read index doesn't point to a hole. */
int pa_rtp_send(pa_rtp_context *c, size_t size, pa_memblockq *q);
pa_rtp_context* pa_rtp_context_init_recv(pa_rtp_context *c, int fd, size_t frame_size);
int pa_rtp_send(pa_rtp_context *c, size_t size, pa_memblockq *q);
pa_rtp_context* pa_rtp_context_init_recv(pa_rtp_context *c, int fd, size_t frame_size);
+ /* FIXME: u->memblockq doesn't have a silence memchunk set, so
+ * pa_memblockq_peek() will return 0 without returning any memblock if the
+ * read index points to a hole. If the memblockq is rewound beyond index 0,
+ * then there will be a hole. */
+ pa_assert(chunk->memblock);
+
chunk->length = PA_MIN(chunk->length, nbytes);
pa_memblockq_drop(u->memblockq, chunk->length);
chunk->length = PA_MIN(chunk->length, nbytes);
pa_memblockq_drop(u->memblockq, chunk->length);