[FFmpeg-devel] [PATCH] avfilter/af_atempo: offset all output timestamps by same amount of first input timestamp
Pavel Koshevoy
pkoshevoy at gmail.com
Wed May 8 06:14:07 EEST 2019
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
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