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

[Pavel Koshevoy]

On 5/7/19 8:41 PM, Pavel Koshevoy wrote:
> 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.
>

However, it might be cleaner to move `atempo->start_pts = AV_NOPTS_VALUE;` from 
config_props to yae_clear