avcodec_parameters_to_context(avctx, st->codecpar);
if( !av_dict_get(copts, "threads", NULL, 0) )
avctx->thread_count = ffmpeg->ff_cpus();
avcodec_parameters_to_context(avctx, st->codecpar);
if( !av_dict_get(copts, "threads", NULL, 0) )
avctx->thread_count = ffmpeg->ff_cpus();