Tool to analyse segments

check_frames.js

/* fastroza@ned.cl
 */

const spawn = require('child_process').spawn;
const frame_regex = /\[FRAME\]\n([\/\w=\n\.:\d\-_\s]*)\[\/FRAME\]\n/g;
const value_regex = /([\w_]*)=([\/\d\.\w_:]*)/g;

function digest_frame(str)
{
	ret = {};
	while ( (match = value_regex.exec(str)) ) {
		ret[match[1]] = match[2];
	}
	return ret;
}

function for_each_frame(str, frame_cb)
{
	while ( (match = frame_regex.exec(str)) ) {
		frame_cb(digest_frame(match[1]));
	}
}

var video_frames = [];
var audio_frames = [];
probe = spawn("/usr/bin/ffprobe", ["-show_frames", process.argv[2]]);
probe.stdout.on('data', (data) => {
	for_each_frame(data, function(frame) {
		if(frame.media_type == 'video') {
			video_frames.push({pts: parseFloat(frame.pkt_pts_time), picture_number: frame.coded_picture_number, duration: parseFloat(frame.pkt_duration_time)});
		} else if(frame.media_type == 'audio') {
			audio_frames.push({pts: parseFloat(frame.pkt_pts_time), duration: parseFloat(frame.pkt_duration_time)});
		}
	});
});

probe.on('close', function() {
	var video_length = 0;
	if(video_frames.length > 2) {
		var duration = video_frames[1].pts - video_frames[0].pts;
		var base = video_frames[0].pts;
		var base_index = 0;
		for(var i in video_frames) {
			var diff = (video_frames[base_index].pts+(i-base_index)*duration) - video_frames[i].pts;
			if(Math.abs(diff) > 0.0001) {
				console.log("VIDEO: PTS " + video_frames[i].pts + " should be " + (video_frames[base_index].pts+(i-base_index)*duration))
				base_index = i;
				base = video_frames[base_index].pts;
			}
		}
		video_length = (video_frames[video_frames.length-1].pts + video_frames[video_frames.length-1].duration - video_frames[0].pts);
	}
	var audio_length = 0;
	if(audio_frames.length > 2) {
		var global_diff = 0;
		var drift = 0;
		console.log("First audio pts: " + audio_frames[0].pts);
                for(i = 0; i < audio_frames.length-1; i++) {
                        var diff = audio_frames[i].pts + drift + audio_frames[i].duration - audio_frames[i+1].pts;
			global_diff += diff;
                        if(Math.abs(diff) > 0.0001) {
                                console.log("AUDIO["+(i+1)+"]: PTS " + audio_frames[i+1].pts + " should be " + (audio_frames[i].pts + drift + audio_frames[i].duration))
                        }
                }
		console.log("Last audio pts: " + audio_frames[audio_frames.length-1].pts, "next frame: " + (audio_frames[audio_frames.length-1].pts + audio_frames[audio_frames.length-1].duration));
		console.log("Global diff: " + global_diff)
		audio_length = (audio_frames[audio_frames.length-1].pts + audio_frames[audio_frames.length-1].duration - audio_frames[0].pts);
	}
	console.log("Video length: ", video_length);
	console.log("Audio length: ", audio_length);
	console.log("length(video)-length(audio): ", video_length - audio_length);
});