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modules: rtp-gstreamer: Fix RTP sound lag

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In the current scenario of reading samples from the appsink, it is
observed that we do not actually read all the data available in the
appsink to read. This results in a choppy sound or heard as gaps in
the playback.

The underlying reason for this happening is as follows. Let's say
the appsink new sample callback is called 2-3 times, but, with the
underlying fdsem post machinery when pa_rtp_recv eventually gets
called, there would be those 2-3 samples to read. However, we were
only reading one sample in the current implementation.

Fix this by reading all samples from the appsink in a loop, coalescing
them and then writing to the memchunk.

Fixes: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/issues/889

Signed-off-by: Sanchayan Maity <sanchayan@asymptotic.io>
This commit is contained in:
Sanchayan Maity 2020-07-28 14:11:05 +05:30 • committed by Arun Raghavan
parent dd70c3c589
commit 1781031c8b
1 changed files with 62 additions and 24 deletions
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86
src/modules/rtp/rtp-gstreamer.c
View file

@ -32,6 +32,7 @@
#include <gst/gst.h>
#include <gst/app/gstappsrc.h>
#include <gst/app/gstappsink.h>
#include <gst/base/gstadapter.h>
#include <gst/rtp/gstrtpbuffer.h>
#define MAKE_ELEMENT_NAMED(v, e, n) \
@ -438,36 +439,73 @@ fail:
/* Called from I/O thread context */
int pa_rtp_recv(pa_rtp_context *c, pa_memchunk *chunk, pa_mempool *pool, uint32_t *rtp_tstamp, struct timeval *tstamp) {
GstSample *sample = NULL;
GstBufferList *buf_list;
GstAdapter *adapter;
GstBuffer *buf;
GstMapInfo info;
void *data;
uint8_t *data;
uint64_t data_len = 0;
if (!process_bus_messages(c))
goto fail;
sample = gst_app_sink_pull_sample(GST_APP_SINK(c->appsink));
if (!sample) {
pa_log_warn("Could not get any more data");
goto fail;
adapter = gst_adapter_new();
pa_assert(adapter);
while (true) {
sample = gst_app_sink_try_pull_sample(GST_APP_SINK(c->appsink), 0);
if (!sample)
break;
buf = gst_sample_get_buffer(sample);
if (GST_BUFFER_IS_DISCONT(buf))
pa_log_info("Discontinuity detected, possibly lost some packets");
if (!gst_buffer_map(buf, &info, GST_MAP_READ)) {
pa_log_info("Failed to map buffer");
gst_sample_unref(sample);
goto fail;
}
data_len += info.size;
/* We need the buffer to be valid longer than the sample, which will
* be valid only for the duration of this loop.
*
* To do this, increase the ref count. Ownership is transferred to the
* adapter in gst_adapter_push.
*/
gst_buffer_ref(buf);
gst_adapter_push(adapter, buf);
gst_buffer_unmap(buf, &info);
gst_sample_unref(sample);
}
buf = gst_sample_get_buffer(sample);
buf_list = gst_adapter_take_buffer_list(adapter, data_len);
pa_assert(buf_list);
if (GST_BUFFER_IS_DISCONT(buf))
pa_log_info("Discontinuity detected, possibly lost some packets");
pa_assert(pa_mempool_block_size_max(pool) >= data_len);
if (!gst_buffer_map(buf, &info, GST_MAP_READ))
goto fail;
pa_assert(pa_mempool_block_size_max(pool) >= info.size);
chunk->memblock = pa_memblock_new(pool, info.size);
chunk->memblock = pa_memblock_new(pool, data_len);
chunk->index = 0;
chunk->length = info.size;
chunk->length = data_len;
data = (uint8_t *) pa_memblock_acquire_chunk(chunk);
for (int i = 0; i < gst_buffer_list_length(buf_list); i++) {
buf = gst_buffer_list_get(buf_list, i);
if (!gst_buffer_map(buf, &info, GST_MAP_READ)) {
gst_buffer_list_unref(buf_list);
goto fail;
}
memcpy(data, info.data, info.size);
data += info.size;
gst_buffer_unmap(buf, &info);
}
data = pa_memblock_acquire_chunk(chunk);
/* TODO: we could probably just provide an allocator and avoid a memcpy */
memcpy(data, info.data, info.size);
pa_memblock_release(chunk->memblock);
/* When buffer-mode = none, the buffer PTS is the RTP timestamp, converted
@ -475,17 +513,17 @@ int pa_rtp_recv(pa_rtp_context *c, pa_memchunk *chunk, pa_mempool *pool, uint32_
* wraparound-corrected, and the DTS is the pipeline clock timestamp from
* when the buffer was acquired at the source (this is actually the running
* time which is why we need to add base time). */
*rtp_tstamp = gst_util_uint64_scale_int(GST_BUFFER_PTS(buf), c->ss.rate, GST_SECOND) & 0xFFFFFFFFU;
pa_timeval_rtstore(tstamp, (GST_BUFFER_DTS(buf) + gst_element_get_base_time(c->pipeline)) / GST_USECOND, false);
*rtp_tstamp = gst_util_uint64_scale_int(GST_BUFFER_PTS(gst_buffer_list_get(buf_list, 0)), c->ss.rate, GST_SECOND) & 0xFFFFFFFFU;
pa_timeval_rtstore(tstamp, (GST_BUFFER_DTS(gst_buffer_list_get(buf_list, 0)) + gst_element_get_base_time(c->pipeline)) / GST_USECOND, false);
gst_buffer_unmap(buf, &info);
gst_sample_unref(sample);
gst_buffer_list_unref(buf_list);
gst_object_unref(adapter);
return 0;
fail:
if (sample)
gst_sample_unref(sample);
if (adapter)
gst_object_unref(adapter);
if (chunk->memblock)
pa_memblock_unref(chunk->memblock);