On Wed, Mar 21, 2018 at 10:46:31PM -0700, mi...@brew.sh wrote: > From: Misty De Meo <mistyde...@gmail.com> [...]
> +static int film_write_header(AVFormatContext *format_context)
> +{
> + int ret = 0;
> + int64_t stabstart_pos, sample_table_size, stabsize, headersize;
> + int8_t audio_codec;
> + AVIOContext *pb = format_context->pb;
> + FILMOutputContext *film = format_context->priv_data;
> + FILMPacket *prev, *packet;
> + AVStream *audio = NULL;
> + AVStream *video = NULL;
> +
> + /* Calculate how much we need to reserve for the header;
> + * this is the amount the rest of the data will be shifted up by. */
> + sample_table_size = film->packet_count * 16;
> + stabsize = 16 + sample_table_size;
> + headersize = 16 + // FILM header base
> + 32 + // FDSC chunk
> + stabsize;
> +
> + ret = shift_data(format_context, headersize);
> + if (ret < 0)
> + return ret;
> + // Seek back to the beginning to start writing the header now
> + avio_seek(pb, 0, SEEK_SET);
> +
> + if (film->audio_index > -1)
> + audio = format_context->streams[film->audio_index];
> + if (film->video_index > -1)
> + video = format_context->streams[film->video_index];
> +
> + if (audio != NULL) {
> + audio_codec = get_audio_codec_id(audio->codecpar->codec_id);
> + if (audio_codec < 0) {
> + av_log(format_context, AV_LOG_ERROR, "Incompatible audio stream
> format.\n");
> + return AVERROR(EINVAL);
> + }
> + }
> +
> + // First, write the FILM header; this is very simple
> +
> + ffio_wfourcc(pb, "FILM");
> + avio_wb32(pb, 48 + stabsize);
> + /* This seems to be okay to hardcode, since this muxer targets 1.09
> features;
> + * videos produced by this muxer are readable by 1.08 and lower players.
> */
> + ffio_wfourcc(pb, "1.09");
> + // I have no idea what this field does, might be reserved
> + avio_wb32(pb, 0);
> +
> + // Next write the FDSC (file description) chunk
> + ffio_wfourcc(pb, "FDSC");
> + avio_wb32(pb, 0x20); // Size of FDSC chunk
> + // TODO stop hardcoding this if support for another codec is added
> + ffio_wfourcc(pb, "cvid");
> + avio_wb32(pb, video->codecpar->height);
> + avio_wb32(pb, video->codecpar->width);
> + avio_w8(pb, 24); // Bits per pixel - observed to always be 24
> +
> + if (audio != NULL) {
> + avio_w8(pb, audio->codecpar->channels); // Audio channels
> + avio_w8(pb, audio->codecpar->bits_per_coded_sample); // Audio bit
> depth
> + avio_w8(pb, audio_codec); // Compression - 0 is PCM, 2 is ADX
> + avio_wb16(pb, audio->codecpar->sample_rate); // Audio sampling rate
> + } else {
> + // Set all these fields to 0 if there's no audio
> + avio_w8(pb, 0);
> + avio_w8(pb, 0);
> + avio_w8(pb, 0);
> + avio_wb16(pb, 0);
> + }
> +
> + // I have no idea what this pair of fields does either, might be reserved
> + avio_wb32(pb, 0);
> + avio_wb16(pb, 0);
> +
> + // Finally, write the STAB (sample table) chunk
> + stabstart_pos = avio_tell(pb);
this is set but never used
[...]
--
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