MPEG-DASH Video

In this topic, you will learn about creating MPEG-DASH renditions for your videos.

Overview

MPEG-DASH is a segmented video format. It is particularly useful if you require DRM security for your content, because DASH can be used with Playready, Marlin, or Widevine Modular DRM. Since the syntax for specifying MPEG-DASH renditions is slightly different than that for other video formats, we include here a couple of sample profiles, one without DRM packaging and the other including DRM packaging.

For details on how Brightcove Player determines which rendition to actually play, please see the Determining Which Rendition Will Play document.

Sample Profile (no DRM)

This sample shows the packaging of MPEG-DASH renditions without DRM packaging.

For DASH renditions, set the decoder_bitrate_cap decoder_buffer_size to optimize playback on your target viewing environments.

Our general recommendation is to set decoder_bitrate_cap to the maximum bitrate available for the video stream. Remember you need to take into account the audio, as well as overhead for the file format. The decoder_buffer_size is technically supposed to match the available video buffer memory on the decoding device, but is often better used to control how much content may be pre-buffered. It works as a multiple of the decoder_bitrate_cap, so that for example, if decoder_bitrate_cap was 500 kbps, and decoder_buffer_size was 1000 kbps, then the buffer could store 2 seconds worth of video. We also recommend setting the video_bitrate a little lower than the decoder_bitrate_cap, which allows the encoder to use more data to encode complex scenes and less data on simpler scenes. A decent starting point would be to assume up to 10% of overhead for the file format, setting the video_bitrate 10% lower than the decoder_bitrate_cap, and allowing about 1.5 seconds of video to be buffered.

Assuming a 1000 Kbps connection is available to the viewer:

1000 * 0.90 = 900 Kbps available after subtracting 10% for format overhead.
900 - 128 = 772 Kbps video decoder_bitrate_cap after subtracting 128 Kbps for the audio.
772 * 1.5 = 1158 Kb decoder_buffer_size (for 1.5 seconds worth of video).
772 * 0.90 = 695 Kbps target video bitrate (10% lower than the decoder_bitrate_cap).

{
  "id": "56e077ace4b0a7b3c178e6e7",
  "name": "DASH-no-drm",
  "description": "DASH renditions",
  "account_id": "1752604059001",
  "renditions": [
    {
      "media_type": "video",
      "id": "56e077ace4b0a7b3c178e6e5",
      "reference_id": "r1",
      "format": "m4f",
      "type": "segmented",
      "audio_codec": "aac",
      "audio_bitrate": 36,
      "video_codec": "h264",
      "video_bitrate": 300,
      "decoder_bitrate_cap": 400,
      "decoder_buffer_size": 800,
      "force_aac_profile": "aac-lc",
      "frame_rate": 30,
      "keyframe_rate": 0.5,
      "fixed_keyframe_interval": true,
      "width": 800,
      "height": 600,
      "h264_profile": "baseline",
      "streaming_delivery_profile": "live"
    },
    {
      "media_type": "video",
      "id": "56e077ace4b0a7b3c178e6e6",
      "reference_id": "r2",
      "format": "m4f",
      "type": "segmented",
      "audio_codec": "aac",
      "audio_bitrate": 36,
      "video_codec": "h264",
      "video_bitrate": 600,
      "decoder_bitrate_cap": 800,
      "decoder_buffer_size": 1600,
      "frame_rate": 30,
      "keyframe_rate": 0.5,
      "fixed_keyframe_interval": true,
      "force_aac_profile": "aac-lc",
      "width": 1024,
      "height": 768,
      "h264_profile": "baseline",
      "streaming_delivery_profile": "live"
    },
    {
      "media_type": "image",
      "id": "559697ece4b072e9641b840f",
      "format": "jpg",
      "label": "poster",
      "width": 640,
      "height": 360
    },
    {
      "media_type": "image",
      "id": "559697ece4b072e9641b8410",
      "format": "jpg",
      "label": "thumbnail",
      "width": 160,
      "height": 90
    }
  ],
  "packages": [
    {
      "package_type": "dash",
      "renditions": [
        "r1"
      ]
    },
    {
      "package_type": "dash",
      "renditions": [
        "r2"
      ]
    }
  ]
}

Sample Profile (with DRM)

Here is the same sample profile with Common Encryption (CENC) and DRM packaging (Widevine and Playready) included.

{
    "account_id": 2728142649001,
    "digital_master": {
        "distribute": true,
        "rendition": "passthrough"
    },
    "name": "dash-cenc-live",
    "description": "This will produce 6 dash live renditions with cenc",
    "renditions": [
        {
            "media_type": "video",
            "reference_id": "av0",
            "format": "m4f",
            "audio_codec": "aac",
            "audio_bitrate": 40,
            "video_bitrate": 110,
            "decoder_bitrate_cap": 200,
            "decoder_buffer_size": 400,
            "width": "400",
            "height": "300",
            "fixed_keyframe_interval": true,
            "frame_rate": 30,
            "force_aac_profile": "aac-lc",
            "video_codec": "h264",
            "h264_profile": "baseline",
            "keyframe_rate": 0.5,
            "streaming_delivery_profile": "live",
            "type": "segmented"
        },
        {
            "media_type": "video",
            "reference_id": "av1",
            "format": "m4f",
            "audio_codec": "aac",
            "audio_bitrate": 40,
            "video_bitrate": 260,
            "decoder_bitrate_cap": 400,
            "decoder_buffer_size": 800,
            "width": "400",
            "height": "300",
            "fixed_keyframe_interval": true,
            "frame_rate": 30,
            "force_aac_profile": "aac-lc",
            "video_codec": "h264",
            "h264_profile": "baseline",
            "keyframe_rate": 0.5,
            "streaming_delivery_profile": "live",
            "type": "segmented"
        },
        {
            "media_type": "video",
            "reference_id": "av2",
            "format": "m4f",
            "audio_codec": "aac",
            "audio_bitrate": 64,
            "video_bitrate": 436,
            "decoder_bitrate_cap": 600,
            "decoder_buffer_size": 1200,
            "width": "480",
            "height": "360",
            "fixed_keyframe_interval": true,
            "frame_rate": 30,
            "force_aac_profile": "aac-lc",
            "video_codec": "h264",
            "h264_profile": "baseline",
            "keyframe_rate": 0.5,
            "streaming_delivery_profile": "live",
            "type": "segmented"
        },
        {
            "media_type": "video",
            "reference_id": "av3",
            "format": "m4f",
            "audio_codec": "aac",
            "audio_bitrate": 96,
            "video_bitrate": 704,
            "decoder_bitrate_cap": 800,
            "decoder_buffer_size": 1600,
            "width": "640",
            "height": "480",
            "fixed_keyframe_interval": true,
            "frame_rate": 30,
            "force_aac_profile": "aac-lc",
            "video_codec": "h264",
            "h264_profile": "baseline",
            "keyframe_rate": 0.5,
            "streaming_delivery_profile": "live",
            "type": "segmented"
        },
        {
            "media_type": "video",
            "reference_id": "av4",
            "format": "m4f",
            "audio_codec": "aac",
            "audio_bitrate": 128,
            "video_bitrate": 1072,
            "decoder_bitrate_cap": 1200,
            "decoder_buffer_size": 2400,
            "width": "720",
            "height": "540",
            "fixed_keyframe_interval": true,
            "frame_rate": 30,
            "force_aac_profile": "aac-lc",
            "video_codec": "h264",
            "h264_profile": "baseline",
            "keyframe_rate": 0.5,
            "streaming_delivery_profile": "live",
            "type": "segmented"
        },
        {
            "media_type": "video",
            "reference_id": "av5",
            "format": "m4f",
            "audio_codec": "aac",
            "audio_bitrate": 128,
            "video_bitrate": 1672,
            "decoder_bitrate_cap": 2000,
            "decoder_buffer_size": 4000,
            "width": "1280",
            "height": "960",
            "fixed_keyframe_interval": true,
            "frame_rate": 30,
            "force_aac_profile": "aac-lc",
            "video_codec": "h264",
            "h264_profile": "baseline",
            "keyframe_rate": 0.5,
            "streaming_delivery_profile": "live",
            "type": "segmented"
        },
        {
            "media_type": "image",
            "format": "png",
            "label": "poster",
            "width": 640,
            "height": 480
        },
        {
            "media_type": "image",
            "format": "png",
            "label": "thumbnail",
            "width": 160,
            "height": 90
        }
    ],
    "packages": [
        {
"drm": [
    "playready",
    "widevine"
],
"package_type": "dash",
"renditions": [
    "av0"
]
        },
        {
"drm": [
    "playready",
    "widevine"
],
"package_type": "dash",
"renditions": [
    "av1"
]
        },
        {
"drm": [
    "playready",
    "widevine"
],
"package_type": "dash",
"renditions": [
    "av2"
]
        },
        {
"drm": [
    "playready",
    "widevine"
],
"package_type": "dash",
"renditions": [
    "av3"
]
        },
        {
"drm": [
    "playready",
    "widevine"
],
"package_type": "dash",
"renditions": [
    "av4"
]
        },
        {
"drm": [
    "playready",
    "widevine"
],
"package_type": "dash",
"renditions": [
    "av5"
]
        }
    ]
}

Silverlight security

On certain platforms, the Brightcove Player uses a Silverlight fallback to play MPEG-DASH renditions. For security reasons, Silverlight requires that a clientaccesspolicy.xml file be present in the document root of the server from which DASH content is served. See this Microsoft article for more details.

Here is a sample clientaccesspolicy.xml file:

Known issues

The Default (Auto Display) caption setting in the Media module's TEXT TRACK section is not supported when used in conjunction with DASH and in-manifest captions. In-manifest captions are used with the Brightcove products Dynamic Delivery and SSAI, for example. A workaround for this issue is to use the <track> tag with the Advanced Brightcove Player implementation. This is detailed in the Adding Captions to Videos Programmatically document. Note you must use the default attribute with the <track> tag.