FAQ

Content Prep

Encoding/transcoding is a pretty complex topic. The FFmpeg/x264/mp4box workflow is generally fine and it is what we use in the Axinom reference encoder. My general suggestions regarding the most critical points in this regard:

• Always use DASH live profile (mp4box -profile "dashavc264:live")
• Ensure that your encoder uses a fixed keyframe distance that is equal to your segment size (or a multiple of which is equal to it); FFmpeg has some defects here leading to bad output; with x264 the following works: --keyint 59 --min-keyint 59 --no-scenecut
• Use dash-strict mode with mp4box if you use fixed keyframe distances (mp4box -dash-strict 4000) - the default dash mode produced unexpected deviations last I tried it
• To avoid FFmpeg being clever with frame drop/duplication, use -vsync passthrough
• Watch out for aspect ratio issues! Not all input content has SAR 1:1!
• Do not use bitstream switching (mp4box -bs-switching no)
• If using encryption, put PSSH box information only in the manifest; (no PSSH data in crypt.xml for mp4box); also mp4box -sample-groups-traf made encrypted video work better in more players but I forget why

Codecs

• Safari <=9 does not support AVC3
• Internet Explorer 11 can play AVC3, but only if you signal to the browser it is AVC1
• MEDIA_ERR_DECODE indicates an issue with your stream, not dash.js.
  • Understanding supported codecs
  • In Chrome, the chrome://media-internals page may help you identify the problem

Browser Support

• Firefox < 49 may sometimes fail to start playback on dynamic streams, or streams with a #t= URL fragment

Networking

• Having the dash.js client use only one TCP session
• Adding headers to requests made by the dash.js client

Flow Chart Diagrams

• Non BOLA ABR Logic
• Scheduling and Buffer Flow