[FFmpeg-devel] [PATCH 1/2] lavd/alsa: fix timestamp calculation

Lukasz M lukasz.m.luki at gmail.com
Sat Oct 26 02:34:00 CEST 2013


On 26 October 2013 01:55, Timothy Gu <timothygu99 at gmail.com> wrote:

> On Oct 25, 2013 4:40 PM, "Lukasz Marek" <lukasz.m.luki at gmail.com> wrote:
> >
> > Current implementation didn't include duration of
> > last processed packet.
> > Device may return negative timestamps without
> > this correction.
> >
> > Signed-off-by: Lukasz Marek <lukasz.m.luki at gmail.com>
> > ---
> >  libavdevice/alsa-audio-enc.c |   12 +++++++++---
> >  libavdevice/alsa-audio.h     |    1 +
> >  2 files changed, 10 insertions(+), 3 deletions(-)
> >
> > diff --git a/libavdevice/alsa-audio-enc.c b/libavdevice/alsa-audio-enc.c
> > index 0f4e4a2..4d0e17b 100644
> > --- a/libavdevice/alsa-audio-enc.c
> > +++ b/libavdevice/alsa-audio-enc.c
> > @@ -79,6 +79,13 @@ static int audio_write_packet(AVFormatContext *s1,
> AVPacket *pkt)
> >      int size     = pkt->size;
> >      uint8_t *buf = pkt->data;
> >
> > +    if (!(s->timestamp_diff = pkt->duration)) {
> > +        AVStream *st = s1->streams[0];
> > +        AVCodecContext *codec_ctx = st->codec;
> > +        /*XXX: no need to recalculate: 1/sample_rate ==
> avprinv_set_pts_info() */
>
> Nit a) typo: avpriv
> Nit b) space between /* and XXX.
>
> > +        s->timestamp_diff = pkt->size /
> (av_get_bytes_per_sample(codec_ctx->sample_fmt) * codec_ctx->channels);
> > +    }
> > +
> >      size /= s->frame_size;
> >      if (s->reorder_func) {
> >          if (size > s->reorder_buf_size)
> > @@ -104,15 +111,14 @@ static int audio_write_packet(AVFormatContext *s1,
> AVPacket *pkt)
> >      return 0;
> >  }
> >
> > -static void
> > -audio_get_output_timestamp(AVFormatContext *s1, int stream,
> > +static void audio_get_output_timestamp(AVFormatContext *s1, int stream,
>
> This should be dropped or be in separate patch.
>
> >      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;
> > +    *dts = s1->streams[0]->cur_dts + s->timestamp_diff - delay;
> >  }
> >
> >  AVOutputFormat ff_alsa_muxer = {
> > diff --git a/libavdevice/alsa-audio.h b/libavdevice/alsa-audio.h
> > index 44b7c72..b9670b9 100644
> > --- a/libavdevice/alsa-audio.h
> > +++ b/libavdevice/alsa-audio.h
> > @@ -57,6 +57,7 @@ typedef struct AlsaData {
> >      void (*reorder_func)(const void *, void *, int);
> >      void *reorder_buf;
> >      int reorder_buf_size; ///< in frames
> > +    int64_t timestamp_diff; ///< duration of last packet, need to
> calculate timestamp
>
> nit: needed to ...
>
> >  } AlsaData;
>

I love typos on the Friday evening :) Fixed patch attached
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