Switch FFmpeg to use raw monotonic timestamps

Use ALSA high resolution hardware timestamps if available

1 files changed, 72 insertions, 0 deletions

diff --git a/libavdevice/alsa.c b/libavdevice/alsa.c
index 117b2ea..10ffe56 100644
--- a/libavdevice/alsa.c
+++ b/libavdevice/alsa.c
@@ -174,6 +174,8 @@ av_cold int ff_alsa_open(AVFormatContext *ctx, snd_pcm_stream_t mode,
     snd_pcm_format_t format;
     snd_pcm_t *h;
     snd_pcm_hw_params_t *hw_params;
+    snd_pcm_sw_params_t *sw_params;
+    snd_pcm_status_t *alsa_pcm_status;
     snd_pcm_uframes_t buffer_size, period_size;
     uint64_t layout = ctx->streams[0]->codecpar->channel_layout;
 
@@ -269,6 +271,72 @@ av_cold int ff_alsa_open(AVFormatContext *ctx, snd_pcm_stream_t mode,
         goto fail;
     }
 
+    s->use_driver_timestamps = 0;
+    if (snd_pcm_hw_params_supports_audio_ts_type(hw_params, 0)) {
+        av_log(ctx, AV_LOG_INFO, "capture device supports compat timestamps\n");
+        s->use_driver_timestamps |= 1;
+    }
+    if (snd_pcm_hw_params_supports_audio_ts_type(hw_params, 1)) {
+        av_log(ctx, AV_LOG_INFO, "capture device supports default timestamps\n");
+        s->use_driver_timestamps |= 2;
+    }
+    if (snd_pcm_hw_params_supports_audio_ts_type(hw_params, 2)) {
+        av_log(ctx, AV_LOG_INFO, "capture device supports link timestamps\n");
+        s->use_driver_timestamps |= 4;
+    }
+    if (snd_pcm_hw_params_supports_audio_ts_type(hw_params, 3)) {
+        av_log(ctx, AV_LOG_INFO, "capture device supports link absolute timestamps\n");
+        s->use_driver_timestamps |= 8;
+    }
+    if (snd_pcm_hw_params_supports_audio_ts_type(hw_params, 4)) {
+        av_log(ctx, AV_LOG_INFO, "capture device supports link estimated timestamps\n");
+        s->use_driver_timestamps |= 16;
+    }
+    if (snd_pcm_hw_params_supports_audio_ts_type(hw_params, 5)) {
+        av_log(ctx, AV_LOG_INFO, "capture device supports link synchronized timestamps\n");
+        s->use_driver_timestamps |= 32;
+    }
+
+    res = snd_pcm_sw_params_malloc(&sw_params);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot allocate software parameter structure (%s)\n",
+               snd_strerror(res));
+        goto fail;
+    }
+
+    res = snd_pcm_sw_params_current(h, sw_params);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot read parameters from device (%s)\n",
+               snd_strerror(res));
+        snd_pcm_sw_params_free(sw_params);
+        goto fail;
+    }
+
+    res = snd_pcm_sw_params_set_tstamp_mode(h, sw_params, SND_PCM_TSTAMP_ENABLE);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot enable timestamps (%s)\n",
+               snd_strerror(res));
+        snd_pcm_sw_params_free(sw_params);
+        goto fail;
+    }
+
+    res = snd_pcm_sw_params_set_tstamp_type(h, sw_params, SND_PCM_TSTAMP_TYPE_MONOTONIC_RAW);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot set timestamp mode (%s)\n",
+               snd_strerror(res));
+        snd_pcm_sw_params_free(sw_params);
+        goto fail;
+    }
+
+    res = snd_pcm_sw_params(h, sw_params);
+    if (res < 0) {
+        av_log(ctx, AV_LOG_ERROR, "cannot set parameters (%s)\n",
+               snd_strerror(res));
+        snd_pcm_sw_params_free(sw_params);
+        goto fail;
+    }
+
+    snd_pcm_sw_params_free(sw_params);
     snd_pcm_hw_params_free(hw_params);
 
     if (channels > 2 && layout) {
@@ -286,7 +354,10 @@ av_cold int ff_alsa_open(AVFormatContext *ctx, snd_pcm_stream_t mode,
         }
     }
 
+    snd_pcm_status_malloc(&alsa_pcm_status);
+
     s->h = h;
+    s->st = alsa_pcm_status;
     return 0;
 
 fail:
@@ -308,6 +379,7 @@ av_cold int ff_alsa_close(AVFormatContext *s1)
     if (CONFIG_ALSA_INDEV)
         ff_timefilter_destroy(s->timefilter);
     snd_pcm_close(s->h);
+    snd_pcm_status_free(s->st);
     return 0;
 }