On Sun, Jul 18, 2021 at 1:21 PM Gyan Doshi <ffm...@gyani.pro> wrote: > > > > On 2021-07-18 10:42, Linjie Fu wrote: > > Hi Gyan, > > On Sun, Jul 18, 2021 at 12:24 PM Gyan Doshi <ffm...@gyani.pro> wrote: > >> > >> > >> On 2021-07-18 09:32, Linjie Fu wrote: > >>> On Wed, Jul 7, 2021 at 9:42 AM Linjie Fu <linjie.justin...@gmail.com> > >>> wrote: > >>>> On Sun, Jul 4, 2021 at 10:50 PM Linjie Fu <fulin...@zju.edu.cn> wrote: > >>>>> From: Linjie Fu <linjie.justin...@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...@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. > >> > > Thanks for the review, tested after applying the readrate patch, I'm > > afraid that it's not identical as hope, > > since ist->nb_packets would increase no matter input stream got output or > > not: > > > > (lldb) p ist->nb_packets > > (uint64_t) $4 = 1 > > > > (lldb) p ist->got_output > > (int) $5 = 0 > > > > Hence we still need to add the check for ist->got_output, or replace > > the ist->nb_packets. > > No, test the speed, not the parity of got_output. got_output is only > incremented when the stream is decoded.
The time interval consumed to get the first frame is tested as well, it's not speeded up: First time to get the frame, it takes 257395 us. After adding the check for got_output in decoding scenery, this would reduce to 48792 us. Hence it doesn't reduce the latency under decode scenery. > Won't work with streamcopy. Got your point. > nb_packets is the correct check since it's incremented after the initial > packet is demuxed. IIRC, the initial packet is demuxed right after the first time we call get_input_packet()-> av_read_frame(), and nb_packets would increase. Hence, the check for ist->nb_packets would reduce the latency for demuxing the first packet, and won't help much if we use start_time like "-ss 30". Under the decoding scenery, we still need to wait until the pkt->pts specified time then demux the packet. If no objections, consider to change the check to: if (!ist->nb_packets || (!ist->got_output && ist->decoding_needed)) continue; to reduce the waiting time for: 1. demuxing the first packet (if any) 2. demuxing the packet before we got the first decoded output. > > Also there is a new warning caught by the check in patchwork, probably > > "mixed declaration and code warning". > > Will send patches to rebase and fix. > > There is already patch for the mixed warning. Saw it, thx. - linjie _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
