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

[Pavel Koshevoy]

On 5/7/19 9:02 PM, Pavel Koshevoy wrote:
> 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
>

also, I am not certain that start_pts and output pts are expressed in the same 
time base... maybe start_pts should be rescaled to output timebase in filter_frame