Opened 6 years ago

Last modified 6 years ago

#8808 new enhancement

Adding CENC ClearKey encryption support to DASH

Reported by: qfsw Owned by:
Priority: wish Component: avformat
Version: git-master Keywords: dash
Cc: Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no

Description

I've been working on modifying FFmpeg to have support for ClearKey CENC encryption when producing MPEG-DASH content but cant quite seem to get it to work

As a test, I've hardcoded the dash encoder to always pass encryption options over to the MP4 muxer, I added the following lines to line 1648 of dashenc.c
​https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/dashenc.c#L1648

av_dict_set(&opts, "encryption_scheme", "cenc-aes-ctr", 0);
av_dict_set(&opts, "encryption_key", "87237D20A19F58A740C05684E699B4AA", 0);
av_dict_set(&opts, "encryption_kid", "A16E402B9056E371F36D348AA62BB749", 0);

I have then built ffmpeg and used it to convert an MP4 file to DASH content, which I then play with the following dash.js player

<!doctype html>
<html>
    <head>
        <title>Dash.js Rocks</title>
        <style>
            video {
                width: 640px;
                height: 360px;
            }
        </style>
    </head>
    <body>
        <div>
            <video id="videoPlayer" controls></video>
        </div>
        <script src="http://cdn.dashjs.org/latest/dash.all.debug.js"></script>
        <script>
            (function(){
                const protData = {
                    "org.w3.clearkey": {
                        "clearkeys": {
                            "oW5AK5BW43HzbTSKpiu3SQ": "hyN9IKGfWKdAwFaE5pm0qg"
                        }
                    }
                };

                var url = "/out/b.mpd";
                var player = dashjs.MediaPlayer().create();
                video = document.querySelector("#videoPlayer");
                player.setProtectionData(protData);
                player.setAutoPlay(false);
                player.initialize(video, url);
            })();
        </script>
    </body>
</html>

This fails to play. The same player does work with both the non modified version of ffmpeg (and hence non encrypted), as well as the output of Bento4
​https://github.com/Dash-Industry-Forum/dash.js/wiki/Generate-MPEG-DASH-content-encrypted-with-MPEG-CENC-ClearKey

With the modified FFmpeg, Opera yields these errors in the console

[169][StreamController] Video Element Error: MEDIA_ERR_DECODE (CHUNK_DEMUXER_ERROR_APPEND_FAILED: Append: stream parsing failed. Data size=3491 append_window_start=0 append_window_end=33.3)

Does anyone have any pointers of anything else that must be done to make this work, or what else I can do to investigate the issue? I thought that perhaps the MPD required modification, but the output from Bento4 has no mentions to the CENC encryption at all and plays correctly

Thanks!

Change History (2)

comment:1 by Chris Miceli, 6 years ago

Can you potentially upload the assets which you used for testing?

The dash specification specifies a "ContentProtection" tag but I'm not sure if it MUST be present vs CAN be present.

comment:2 by Carl Eugen Hoyos, 6 years ago

Component: ffmpeg → avformat
Keywords: cenc removed
Priority: normal → wish
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