[FFmpeg-devel] [PATCH] avfilter/af_atempo: offset all output timestamps by same amount of first input timestamp

[Pavel Koshevoy]

On 5/6/19 6:41 AM, Paul B Mahol wrote:
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
> Makes ffplay display correct timestamps when seeking.
> ---
>   libavfilter/af_atempo.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/libavfilter/af_atempo.c b/libavfilter/af_atempo.c
> index bfdad7d76b..6a23d59641 100644
> --- a/libavfilter/af_atempo.c
> +++ b/libavfilter/af_atempo.c
> @@ -103,6 +103,9 @@ typedef struct ATempoContext {
>       // 1: output sample position
>       int64_t position[2];
>   
> +    // first input timestamp, all other timestamps are offset by this one
> +    int64_t start_pts;
> +
>       // sample format:
>       enum AVSampleFormat format;
>   
> @@ -1055,6 +1058,7 @@ static int config_props(AVFilterLink *inlink)
>       enum AVSampleFormat format = inlink->format;
>       int sample_rate = (int)inlink->sample_rate;
>   
> +    atempo->start_pts = AV_NOPTS_VALUE;
>       return yae_reset(atempo, format, sample_rate, inlink->channels);
>   }
>   
> @@ -1068,7 +1072,7 @@ static int push_samples(ATempoContext *atempo,
>       atempo->dst_buffer->nb_samples  = n_out;
>   
>       // adjust the PTS:
> -    atempo->dst_buffer->pts =
> +    atempo->dst_buffer->pts = atempo->start_pts +
>           av_rescale_q(atempo->nsamples_out,
>                        (AVRational){ 1, outlink->sample_rate },
>                        outlink->time_base);
> @@ -1097,6 +1101,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *src_buffer)
>       const uint8_t *src = src_buffer->data[0];
>       const uint8_t *src_end = src + n_in * atempo->stride;
>   
> +    if (atempo->start_pts == AV_NOPTS_VALUE)
> +        atempo->start_pts = src_buffer->pts;
>       while (src < src_end) {
>           if (!atempo->dst_buffer) {
>               atempo->dst_buffer = ff_get_audio_buffer(outlink, n_out);



I was able to confirm from the debugger that af_atempo.c:config_props gets 
called and atempo->start_pts is reset when seeking in ffplay, so the patch looks 
okay to me.

Thank you,
     Pavel.