FFMPEG plugin does not support virtual stack slice deletion

[imagejan]

See this forum post.

The deleteSlice method likely need to be overridden in this code:

scifio-javacv/plugin/src/main/java/fiji/ffmpeg/IO.java

Lines 151 to 212 in 2aab1e2

	ImageStack stack = new VirtualStack(codecContext.width, codecContext.height, null, null) {
	int previousSlice = -1;
	long frameDuration = guessFrameDuration();
	@Override
	public void finalize() {
	free();
	}
	@Override
	public int getSize() {
	int size = (int)(stream.duration / frameDuration);
	if (last >= 0)
	size = Math.min(last, size);
	if (first > 0)
	size -= first;
	return size;
	}
	@Override
	public String getSliceLabel(int slice) {
	return ""; // maybe calculate the time?
	}
	public long guessFrameDuration() {
	if (avFormat.av_read_frame(formatContext, packet) < 0)
	return 1;
	long firstPTS = packet.pts;
	int frameCount = 5;
	for (int i = 0; i < frameCount; previousSlice = i++)
	if (avFormat.av_read_frame(formatContext, packet) < 0)
	return 1;
	return (packet.pts - firstPTS) / frameCount;
	}
	// TODO: cache two
	@Override
	public ImageProcessor getProcessor(int slice) {
	long time = (first + slice - 1) * frameDuration;
	if (time > 0)
	time -= frameDuration / 2;
	if (stream.start_time != 0x8000000000000000l /* TODO: AVUTIL.AV_NOPTS_VALUE */)
	time += stream.start_time;
	if (previousSlice != slice - 1)
	avFormat.av_seek_frame(formatContext, videoStreamIndex, time,
	AVFORMAT.AVSEEK_FLAG_BACKWARD);
	for (;;) {
	if (avFormat.av_read_frame(formatContext, packet) < 0) {
	packet.data = null;
	packet.size = 0;
	break;
	}
	if (packet.stream_index != videoStreamIndex)
	continue;
	if (previousSlice == slice - 1 || packet.pts >= time)
	break;
	avCodec.avcodec_decode_video2(codecContext, frame, gotPicture, packet);
	}
	previousSlice = slice;
	return readOneFrame(packet);
	}
	};

Related to the plugin served via the FFMPEG update site, corresponding to this branch:
https://github.com/scifio/scifio-javacv/tree/ffmpeg/plugin/src/main/java/fiji/ffmpeg

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/ffmpeg-plugin-does-not-support-virtual-stack-slice-deletion/81112/2