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

[Timothy Gu]

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;
>
>  /**
> --
> 1.7.10.4
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel