FFMPEG Internals: Which Parameters Matter

From libavcodec\uils.c:
int avcodec_parameters_to_context(AVCodecContext *codec,
const AVCodecParameters *par)
{
codec->codec_type = par->codec_type;
codec->codec_id = par->codec_id;
codec->codec_tag = par->codec_tag;
codec->bit_rate = par->bit_rate;
codec->bits_per_coded_sample = par->bits_per_coded_sample;
codec->bits_per_raw_sample = par->bits_per_raw_sample;
codec->profile = par->profile;
codec->level = par->level;
switch (par->codec_type) {
case AVMEDIA_TYPE_VIDEO:
codec->pix_fmt = par->format;
codec->width = par->width;
codec->height = par->height;
codec->field_order = par->field_order;
codec->color_range = par->color_range;
codec->color_primaries = par->color_primaries;
codec->color_trc = par->color_trc;
codec->colorspace = par->color_space;
codec->chroma_sample_location = par->chroma_location;
codec->sample_aspect_ratio = par->sample_aspect_ratio;
codec->has_b_frames = par→video_delay;
break;
case AVMEDIA_TYPE_AUDIO:
codec->sample_fmt = par->format;
codec->channel_layout = par->channel_layout;
codec->channels = par->channels;
codec->sample_rate = par->sample_rate;
codec->block_align = par->block_align;
codec->frame_size = par->frame_size;
codec->delay =
codec->initial_padding = par->initial_padding;
codec->trailing_padding = par->trailing_padding;
codec->seek_preroll = par→seek_preroll;
break;
case AVMEDIA_TYPE_SUBTITLE:
codec->width = par->width;
codec->height = par→height;
break;
}
if (par->extradata) {
av_freep(&codec->extradata);
codec->extradata = av_mallocz(par->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
if (!codec->extradata)
return AVERROR(ENOMEM);
memcpy(codec->extradata, par->extradata, par->extradata_size);
codec->extradata_size = par→extradata_size;
}
return 0;
}

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