ALSA: implement get_output_timestamp.

libavdevice/alsa-audio-enc.c

@@ -102,6 +102,17 @@ static int audio_write_packet(AVFormatContext *s1, AVPacket *pkt)
     return 0;
 }
 
+static void
+audio_get_output_timestamp(AVFormatContext *s1, int stream,
+    int64_t *dts, int64_t *wall)
+{
+    AlsaData *s  = s1->priv_data;
+    snd_pcm_sframes_t delay = 0;
+    *wall = av_gettime();
+    snd_pcm_delay(s->h, &delay);
+    *dts = s1->streams[0]->cur_dts - delay;
+}
+
 AVOutputFormat ff_alsa_muxer = {
     "alsa",
     NULL_IF_CONFIG_SMALL("ALSA audio output"),
@@ -113,5 +124,6 @@ AVOutputFormat ff_alsa_muxer = {
     audio_write_header,
     audio_write_packet,
     ff_alsa_close,
+    .get_output_timestamp = audio_get_output_timestamp,
     .flags = AVFMT_NOFILE,
 };