[FFmpeg-devel] [PATCH] pulse: set default frame_size to 4608

[Federico Simoncelli]

Given the current defaults (channels = 2, sample_rate = 48000) the
frame_size is changed to 4608 in order to obtain whole numbers for
frame_duration (both 16 and 24 bits_per_sample).

 frame_duration = (frame_size * 1000000 * 8) /
                  (sample_rate * channels * bits_per_sample)

A message has been added to warn the user when the frame duration
is not an integer.

Signed-off-by: Federico Simoncelli <fsimonce at redhat.com>
---
 libavdevice/pulse_audio_dec.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/libavdevice/pulse_audio_dec.c b/libavdevice/pulse_audio_dec.c
index 639b381..289b91c3 100644
--- a/libavdevice/pulse_audio_dec.c
+++ b/libavdevice/pulse_audio_dec.c
@@ -55,6 +55,7 @@ static av_cold int pulse_read_header(AVFormatContext *s)
     AVStream *st;
     char *device = NULL;
     int ret;
+    float frame_duration;
     enum AVCodecID codec_id =
         s->audio_codec_id == AV_CODEC_ID_NONE ? DEFAULT_CODEC_ID : s->audio_codec_id;
     const pa_sample_spec ss = { ff_codec_id_to_pulse_format(codec_id),
@@ -93,8 +94,15 @@ static av_cold int pulse_read_header(AVFormatContext *s)
     avpriv_set_pts_info(st, 64, 1, 1000000);  /* 64 bits pts in us */
 
     pd->pts = AV_NOPTS_VALUE;
-    pd->frame_duration = (pd->frame_size * 1000000LL * 8) /
+    frame_duration = (pd->frame_size * 1000000.0F * 8) /
         (pd->sample_rate * pd->channels * av_get_bits_per_sample(codec_id));
+    pd->frame_duration = frame_duration;
+
+    if (pd->frame_duration != frame_duration) {
+        av_log(s, AV_LOG_WARNING, "non-integer frame_duration %.1f will "
+            "produce uneven pts intervals, adjust frame_size (current "
+            "value is %i)\n", frame_duration, pd->frame_size);
+    }
 
     return 0;
 }
@@ -149,7 +157,7 @@ static const AVOption options[] = {
     { "stream_name",   "set stream description",                            OFFSET(stream_name),   AV_OPT_TYPE_STRING, {.str = "record"}, 0, 0, D },
     { "sample_rate",   "set sample rate in Hz",                             OFFSET(sample_rate),   AV_OPT_TYPE_INT,    {.i64 = 48000},    1, INT_MAX, D },
     { "channels",      "set number of audio channels",                      OFFSET(channels),      AV_OPT_TYPE_INT,    {.i64 = 2},        1, INT_MAX, D },
-    { "frame_size",    "set number of bytes per frame",                     OFFSET(frame_size),    AV_OPT_TYPE_INT,    {.i64 = 1024},     1, INT_MAX, D },
+    { "frame_size",    "set number of bytes per frame",                     OFFSET(frame_size),    AV_OPT_TYPE_INT,    {.i64 = 4608},     1, INT_MAX, D },
     { "fragment_size", "set buffering size, affects latency and cpu usage", OFFSET(fragment_size), AV_OPT_TYPE_INT,    {.i64 = -1},      -1, INT_MAX, D },
     { NULL },
 };
-- 
1.8.4.2