lavd/pulse_audio_enc: add buffer size control options

Add options to control the size of the PulseAudio buffer.
Signed-off-by: Lukasz Marek <lukasz.m.luki@gmail.com>
Signed-off-by: Stefano Sabatini <stefasab@gmail.com>

doc/outdevs.texi

@@ -164,6 +164,19 @@ by default it is set to the specified output name.
 Specify the device to use. Default device is used when not provided.
 List of output devices can be obtained with command @command{pactl list sinks}.
 
+@item buffer_size
+@item buffer_duration
+Control the size and duration of the PulseAudio buffer. A small buffer
+gives more control, but requires more frequent updates.
+
+@option{buffer_size} specifies size in bytes while
+@option{buffer_duration} specifies duration in milliseconds.
+
+When both options are provided then the highest value is used
+(duration is recalculated to bytes using stream parameters). If they
+are set to 0 (which is default), the device will use the default
+PulseAudio duration value. By default PulseAudio set buffer duration
+to around 2 seconds.
 @end table
 
 @subsection Examples

libavdevice/pulse_audio_enc.c

@@ -35,6 +35,8 @@ typedef struct PulseData {
     const char *device;
     pa_simple *pa;
     int64_t timestamp;
+    int buffer_size;
+    int buffer_duration;
 } PulseData;
 
 static av_cold int pulse_write_header(AVFormatContext *h)
@@ -59,6 +61,19 @@ static av_cold int pulse_write_header(AVFormatContext *h)
             stream_name = "Playback";
     }
 
+    if (s->buffer_duration) {
+        int64_t bytes = s->buffer_duration;
+        bytes *= st->codec->channels * st->codec->sample_rate *
+                 av_get_bytes_per_sample(st->codec->sample_fmt);
+        bytes /= 1000;
+        attr.tlength = FFMAX(s->buffer_size, av_clip64(bytes, 0, UINT32_MAX - 1));
+        av_log(s, AV_LOG_DEBUG,
+               "Buffer duration: %ums recalculated into %"PRId64" bytes buffer.\n",
+               s->buffer_duration, bytes);
+        av_log(s, AV_LOG_DEBUG, "Real buffer length is %u bytes\n", attr.tlength);
+    } else if (s->buffer_size)
+        attr.tlength = s->buffer_size;
+
     ss.format = ff_codec_id_to_pulse_format(st->codec->codec_id);
     ss.rate = st->codec->sample_rate;
     ss.channels = st->codec->channels;
@@ -142,6 +157,8 @@ static const AVOption options[] = {
     { "name",          "set application name",   OFFSET(name),        AV_OPT_TYPE_STRING, {.str = LIBAVFORMAT_IDENT},  0, 0, E },
     { "stream_name",   "set stream description", OFFSET(stream_name), AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, E },
     { "device",        "set device name",        OFFSET(device),      AV_OPT_TYPE_STRING, {.str = NULL}, 0, 0, E },
+    { "buffer_size",   "set buffer size in bytes", OFFSET(buffer_size), AV_OPT_TYPE_INT,  {.i64 = 0}, 0, INT_MAX, E },
+    { "buffer_duration", "set buffer duration in millisecs", OFFSET(buffer_duration), AV_OPT_TYPE_INT, {.i64 = 0}, 0, INT_MAX, E },
     { NULL }
 };
 

libavdevice/version.h

@@ -29,7 +29,7 @@
 
 #define LIBAVDEVICE_VERSION_MAJOR  55
 #define LIBAVDEVICE_VERSION_MINOR   5
-#define LIBAVDEVICE_VERSION_MICRO 101
+#define LIBAVDEVICE_VERSION_MICRO 102
 
 #define LIBAVDEVICE_VERSION_INT AV_VERSION_INT(LIBAVDEVICE_VERSION_MAJOR, \
                                                LIBAVDEVICE_VERSION_MINOR, \