Method add_video_stream

src/FFmpegWriter.cpp:1146–1337

Add a video output stream

// Add a video output stream
AVStream *FFmpegWriter::add_video_stream() {
	// Find the video codec
	const AVCodec *codec = avcodec_find_encoder_by_name(info.vcodec.c_str());
	if (codec == NULL)
		throw InvalidCodec("A valid video codec could not be found for this file.", path);

	// Free any previous memory allocations
	if (video_codec_ctx != nullptr) {
		AV_FREE_CONTEXT(video_codec_ctx);
	}

	// Create a new video stream
	AVStream* st = avformat_new_stream(oc, codec);
	if (!st)
		throw OutOfMemory("Could not allocate memory for the video stream.", path);

	// Allocate a new codec context for the stream
	ALLOC_CODEC_CTX(video_codec_ctx, codec, st)
#if (LIBAVFORMAT_VERSION_MAJOR >= 58)
	st->codecpar->codec_id = codec->id;
#endif

	AVCodecContext* c = video_codec_ctx;

	c->codec_id = codec->id;
	c->codec_type = AVMEDIA_TYPE_VIDEO;

	// Set sample aspect ratio
	c->sample_aspect_ratio.num = info.pixel_ratio.num;
	c->sample_aspect_ratio.den = info.pixel_ratio.den;

	/* Init video encoder options */
	if (info.video_bit_rate >= 1000
#if (LIBAVCODEC_VERSION_MAJOR >= 58)
		&& c->codec_id != AV_CODEC_ID_AV1
#endif
		) {
		c->bit_rate = info.video_bit_rate;
		if (info.video_bit_rate >= 1500000) {
			if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO)  {
				c->qmin = 2;
				c->qmax = 30;
			}
		}
		// Here should be the setting for low fixed bitrate
		// Defaults are used because mpeg2 otherwise had problems
	} else {
		// Check if codec supports crf or qp
		switch (c->codec_id) {
#if (LIBAVCODEC_VERSION_MAJOR >= 58)
			// FFmpeg 4.0+
			case AV_CODEC_ID_AV1 :
			// TODO: Set `crf` or `qp` according to bitrate, as bitrate is not supported by these encoders yet.
			if (info.video_bit_rate >= 1000) {
				c->bit_rate = 0;
				if (strstr(info.vcodec.c_str(), "aom") != NULL) {
					int calculated_quality = 35;
					if (info.video_bit_rate < 500000) calculated_quality = 50;