extract_keyframe_regions()

std::vector< FileRegion > MayaFlux::IO::VideoStreamContext::extract_keyframe_regions

(

const FFmpegDemuxContext &

demux

)

const

Extract keyframe positions as FileRegion entries.

Parameters

demux

The demux context.

Returns

Vector of FileRegion with type="keyframe".

Definition at line 434 of file VideoStreamContext.cpp.

{
    std::vector<FileRegion> regions;
    if (stream_index < 0 || !codec_context)
        return regions;
 
    AVStream* stream = demux.get_stream(stream_index);
    if (!stream)
        return regions;
 
    AVPacket* pkt = av_packet_alloc();
    if (!pkt)
        return regions;
 
    int idx = 0;
    while (av_read_frame(demux.format_context, pkt) >= 0) {
        if (pkt->stream_index == stream_index && (pkt->flags & AV_PKT_FLAG_KEY)) {
            FileRegion r;
            r.type = "keyframe";
            r.name = "keyframe_" + std::to_string(idx);
 
            int64_t pts = pkt->pts != AV_NOPTS_VALUE ? pkt->pts : pkt->dts;
            double ts = 0.0;
            if (pts != AV_NOPTS_VALUE && stream->time_base.num > 0 && stream->time_base.den > 0)
                ts = static_cast<double>(pts) * av_q2d(stream->time_base);
 
            uint64_t frame_pos = 0;
            if (frame_rate > 0.0)
                frame_pos = static_cast<uint64_t>(ts * frame_rate);
 
            r.start_coordinates = { frame_pos };
            r.end_coordinates = { frame_pos };
            r.attributes["pts"] = pts;
            r.attributes["timestamp_seconds"] = ts;
            r.attributes["keyframe_index"] = idx;
 
            regions.push_back(std::move(r));
            ++idx;
        }
        av_packet_unref(pkt);
    }
 
    av_packet_free(&pkt);
 
    av_seek_frame(demux.format_context, stream_index, 0, AVSEEK_FLAG_BACKWARD);
 
    return regions;
}

References MayaFlux::IO::FileRegion::attributes, codec_context, MayaFlux::IO::FileRegion::end_coordinates, MayaFlux::IO::FFmpegDemuxContext::format_context, frame_rate, MayaFlux::IO::FFmpegDemuxContext::get_stream(), MayaFlux::IO::FileRegion::name, MayaFlux::IO::FileRegion::start_coordinates, stream_index, and MayaFlux::IO::FileRegion::type.

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