HTML5 <audio>/<video> and live transcoding with FFMPEG

video audio html ffmpeg transcoding

15,839

Solution 1

I recently run into the same issue since I want to serve my library to browsers. Surprisingly, the idea to send the stream through ffmpeg and deliver on the fly works quite well. The primary problem was to support seeking...

Following, you find code sniplets in Python using Flask to solve the problem:

We need a function to stream the content:

@app.route('/media/<path:path>.ogv')
def media_content_ogv(path):
    d= os.path.abspath( os.path.join( config.media_folder, path ) )
    if not os.path.isfile( d ): abort(404)
    start= request.args.get("start") or 0
    def generate():
        cmdline= list()
        cmdline.append( config.ffmpeg )
        cmdline.append( "-i" )
        cmdline.append( d );
        cmdline.append( "-ss" )
        cmdline.append( str(start) );
        cmdline.extend( config.ffmpeg_args )
        print cmdline
        FNULL = open(os.devnull, 'w')
        proc= subprocess.Popen( cmdline, stdout=subprocess.PIPE, stderr=FNULL )
        try:
            f= proc.stdout
            byte = f.read(512)
            while byte:
                yield byte
                byte = f.read(512)
        finally:
            proc.kill()

    return Response(response=generate(),status=200,mimetype='video/ogg',headers={'Access-Control-Allow-Origin': '*', "Content-Type":"video/ogg","Content-Disposition":"inline","Content-Transfer-Enconding":"binary"})

Then we need a function to return the duration:

@app.route('/media/<path:path>.js')
def media_content_js(path):
    d= os.path.abspath( os.path.join( config.media_folder, path ) )
    if not os.path.isfile( d ): abort(404)
    cmdline= list()
    cmdline.append( config.ffmpeg )
    cmdline.append( "-i" )
    cmdline.append( d );
    duration= -1
    FNULL = open(os.devnull, 'w')
    proc= subprocess.Popen( cmdline, stderr=subprocess.PIPE, stdout=FNULL )
    try:
        for line in iter(proc.stderr.readline,''):
            line= line.rstrip()
            #Duration: 00:00:45.13, start: 0.000000, bitrate: 302 kb/s
            m = re.search('Duration: (..):(..):(..)\...', line)
            if m is not None: duration= int(m.group(1)) * 3600 + int(m.group(2)) * 60 + int(m.group(3)) + 1
    finally:
        proc.kill()

    return jsonify(duration=duration)

And finally, we hack that into HTML5 using videojs:

<!DOCTYPE html>
<html>
<head>
    <link href="//vjs.zencdn.net/4.5/video-js.css" rel="stylesheet">
    <script src="//vjs.zencdn.net/4.5/video.js"></script>
    <script src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
</head>
<body>
    <video id="video" class="video-js vjs-default-skin" controls preload="auto" width="640" height="264">
    </video>
    <script>
        var video= videojs('video');
        video.src("media/testavi.avi.ogv");

        // hack duration
        video.duration= function() { return video.theDuration; };
        video.start= 0;
        video.oldCurrentTime= video.currentTime;
        video.currentTime= function(time) 
        { 
            if( time == undefined )
            {
                return video.oldCurrentTime() + video.start;
            }
            console.log(time)
            video.start= time;
            video.oldCurrentTime(0);
            video.src("media/testavi.avi.ogv?start=" + time);
            video.play();
            return this;
        };

        $.getJSON( "media/testavi.avi.js", function( data ) 
        {
            video.theDuration= data.duration;
        });
    </script>
</body>

A working example can be found at https://github.com/derolf/transcoder .

dero

Solution 2

Thanks for the reply Camilo. I took a closer look at the HTTP spec regarding the Range request and found:

The header SHOULD indicate the total length of the full entity-body, unless
this length is unknown or difficult to determine. The asterisk "*" character
means that the instance-length is unknown at the time when the response was
generated.

So it's really just a matter of testing how the browsers react when replying with a Content-Range: bytes 0-1/*, for example. I'll let you know what happens.

15,839

Author by

TooTallNate

Programmer / Nerd. @nodejs core committer. JavaScript engineer at @automattic (formerly @Cloudup). Before you ask, I'm 6’6”…

Updated on June 06, 2022

Comments

TooTallNate almost 2 years

So from my web server, I would like to use FFMPEG to transcode a media file for use with an HTML <audio> or <video> tag. Easy enough right?

The conversion would need to take place in real-time, when an HTTP client requested the converted file. Ideally the file would be streamed back to the HTTP client as it is being transcoded (and not afterwards at the end, since that would potentially take a while before any data starts being sent back).

This would be fine, except that in today's browsers, an HTML5 audio or video tag requests the media file in multiple HTTP requests with the Range header. See this question for details.

In that question linked above, you can see that Safari requests weird chunks of the file, including the ending few bytes. This poses a problem in that the web server WOULD have to wait for the conversion to finish, in order to deliver the final bytes of the file to conform to the Range request.

So my question is, is my train of thought right? Is there a better way to deliver transcoding content to an <audio> or <video> tag that wouldn't involve waiting for the entire conversion to finish? Thanks in advance!
jocull almost 11 years

How did you find the compatability with this approach? Did it work well across browsers? Last time I did this I found it was better to take a "guess" at the length and zero-fill the remainder by guessing large. This seems to work with constant bitrates decently.
TooTallNate over 10 years

I never ended up trying to be honest. Anybody else know? Since the spec specifies it it may work out, but it's such a niche part of the spec that we might need to open issues on the various browsers' bug trackers to get it working properly.
Gustav P Svensson almost 4 years

This helped me so much! I am doing the same thing but with node, I just translated your python code to node and also changed some errors in the javascript (oldCurrentTime is not a function). It finally works now, after trying to implement seek for 2 whole days. Thank you!