[FFmpeg-devel] [PATCH v2] fftools/ffmpeg: accelerate seeking while reading input at native frame rate

[Gyan Doshi]

On 2021-07-18 09:32, Linjie Fu wrote:
> On Wed, Jul 7, 2021 at 9:42 AM Linjie Fu <linjie.justin.fu at gmail.com> wrote:
>> On Sun, Jul 4, 2021 at 10:50 PM Linjie Fu <fulinjie at zju.edu.cn> wrote:
>>> From: Linjie Fu <linjie.justin.fu at gmail.com>
>>>
>>> Skip the logic of frame rate emulation until the input reaches the
>>> specified start time.
>>>
>>> Test CMD:
>>>     $ffmpeg -re -ss 30 -i input.mp4 -pix_fmt yuv420p -f sdl2 -
>>>
>>> Before the patch:
>>> first time to got frame, it takes 257305 us
>>> After this patch:
>>> first time to got frame, it takes 48879 us
>>>
>>> Signed-off-by: Linjie Fu <linjie.justin.fu at gmail.com>
>>> ---
>>> [v2]: fixed the mixed declaration and code warning
>>> Calculate the time to get the first frame:
>>> https://github.com/fulinjie/ffmpeg/commit/2aa4762e1e65709997b1ab9dd596332244db80ed
>>>   fftools/ffmpeg.c | 8 ++++++--
>>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
>>> index e97d879cb3..c8849e4250 100644
>>> --- a/fftools/ffmpeg.c
>>> +++ b/fftools/ffmpeg.c
>>> @@ -4221,10 +4221,14 @@ static int get_input_packet(InputFile *f, AVPacket **pkt)
>>>   {
>>>       if (f->rate_emu) {
>>>           int i;
>>> +        int64_t pts;
>>> +        int64_t now;
>>>           for (i = 0; i < f->nb_streams; i++) {
>>>               InputStream *ist = input_streams[f->ist_index + i];
>>> -            int64_t pts = av_rescale(ist->dts, 1000000, AV_TIME_BASE);
>>> -            int64_t now = av_gettime_relative() - ist->start;
>>> +            if (!ist->got_output)
>>> +                continue;
>>> +            pts = av_rescale(ist->dts, 1000000, AV_TIME_BASE);
>>> +            now = av_gettime_relative() - ist->start;
>>>               if (pts > now)
>>>                   return AVERROR(EAGAIN);
>>>           }
>>> --
>>> 2.31.1
>> ping, thx.
>>
> Another ping, thx.

I pushed changes to this code yesterday. I don't think it's required 
anymore, but do test.

Regards,
Gyan