How to fix CHUNK_DEMUXER_ERROR_APPEND_FAILED error when append chunk?

Question

I want to create a video player that can play multiple resolution, so I have to load chunks of different codecs.

I tried to append chunk of the same codec and it work. So I tried to use changeType() but when I append the new codec chunk in the video element I found this error "CHUNK_DEMUXER_ERROR_APPEND_FAILED: Append: stream parsing failed.".

const myMediaSource = new MediaSource();
var videoSourceBuffer;
var quality=480,qlast=480;
var currentSegment = 0;
var loading = false;

function videos() {
    myMediaSource.addEventListener('sourceopen', sourceOpen, { once: true});
}

function sourceOpen() {
    setInterval(feedVideo, 500);
}

function feedVideo() {
    if (!loading) {
        try {
            if (myMediaSource.sourceBuffers.length == 0) {
                videoSourceBuffer = myMediaSource.addSourceBuffer('video/mp4; codecs="avc1.64001E,mp4a.40.2"');
                appendSegment("cinit.mp4", 0);
                first = true;
            } else {
                if (qlast != quality) {
                    videoSourceBuffer = myMediaSource.sourceBuffers[0];
                    if (quality == 1080) {
                        type = 'video/mp4; codecs="avc1.640028,mp4a.40.2"';
                    }
                    else if (quality == 720) {
                        type = 'video/mp4; codecs="avc1.64001F,mp4a.40.2"';
                    }
                    else if (quality == 480) {
                        type = 'video/mp4; codecs="avc1.64001E,mp4a.40.2"';
                    }
                    else if (quality == 360) {
                        type = 'video/mp4; codecs="avc1.64001E,mp4a.40.2"';
                    }
                    videoSourceBuffer.changeType(type);
                    videoSourceBuffer.mode = "segments";
                    qlast = quality;
                }
            }
            if (!first) {
                appendSegment("c" + currentSegment + ".m4s", currentSegment);
            }
            else {
                first = false;
            }
        } catch (error) {
            console.log('Error! ' + error);
        }
    }
}

function appendSegment(file, resourcesIndex) {
    loading = true;
    fetch("http://mysite/video/" + quality + "p/" + file).then(function (response) {
        return response.arrayBuffer();
    }).then(function (videoData) {
        videoSourceBuffer.appendBuffer(videoData);
        videoSourceBuffer.addEventListener('updateend', function () {
        loading = false;
        }, { once: true });
    });
}

How can I fix it?

Answer 1

You almost certainly don't need to use changeType here, since that is typically used for changing codec (eg avc -> hevc) or container (eg mp4 -> webm), whereas you are simply switching within the same codec and container.

The problem is almost certainly that you aren't appending an initialisation segment on a quality change - you only do this for the first quality level.

Fix: insert an appropriate initialisation segment before the first media segment of each new quality.