Hi gentlemen, Please, help us with the following question: What is the best way to force an EXACTLY constant video segment duration? We need the solution urgently.
Best regards, Andrey. On Thu, Aug 15, 2013 at 2:29 PM, Andrey Mochenov <[email protected]>wrote: > Hi, > > We are using FFmpeg libraries git-ee94362 libavformat v55.2.100. > Our purpose is to mux two streams (video and audio) into M3U8 playlist > using HLS. > In addition, we want the duration of every TS segment file be exactly 3.0 > sec (frame rate is 25 fps). > To reach it, we are trying to set several options and properties, namely: > - segment_time > - keyint_min > - scenechange_threshold > - gop_size > - force_key_frames. > > And our code looks as below: > > AVCodecContext *codec_ctx = NULL; > AVFormatContext *ofmt_ctx = NULL; > int ret = 0, gopSize = (int)(3.0 * 25); // 3 sec * 25 fps > > // ofmt_ctx and codec_ctx initialization and filling are OK, but: > > codec_ctx->time_base.num = 1; > codec_ctx->time_base.den = 25 // fps > > // It seems, that the following three lines have no effect without > explisit setting of the "hls_time" property > codec_ctx->keyint_min = gopSize; // in FFMpeg application, the > corresponding option is "-keyint_min 3" > codec_ctx->scenechange_threshold = 0; // in FFMpeg application, the > corresponding option is "-sc_threshold 0" > codec_ctx->gop_size = gopSize; // in FFMpeg application, the > corresponding option is "-g 3" > > ret = av_opt_set_double(ofmt_ctx, "hls_time", 3.0, AV_OPT_SEARCH_CHILDREN); > > // Any of the following lines causes "Option not found" error. > ret = av_opt_set(codec_ctx->priv_data, "profile", "main", > AV_OPT_SEARCH_CHILDREN); > ret = av_opt_set(codec_ctx->priv_data, "preset", "ultrafast", > AV_OPT_SEARCH_CHILDREN); > ret = av_opt_get(ofmt_ctx, "segment_time", AV_OPT_SEARCH_CHILDREN, &str); > ret = av_opt_set((ofmt_ctx, "segment_time", "3.0", AV_OPT_SEARCH_CHILDREN); > > Anyway, the TS files durations are different, (~2-3 sec), and not EXACTLY > 3.0 sec. > Our question: What is the best way to solve the problem? > > Andrey Mochenov. >
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