Step B: Format the source media - Elemental Inference
Format requirementsExample

Step B: Format the source media

Make sure that the source media meets the requirements.

Format requirements

You must format the source media according to the CMAF Ingest (Interface-1) version 1.2 specification.

The following table identifies specific requirements for Elemental Inference.

Characteristic Requirement

Media fragments

Fragmented CMAF Ingest containerized media fragments

MovieFragmentBox

One per segment

Initialization segment: naming

Include an initialization segment with each stream, as follows:

  • For video: Streams(default-video.cmfv)/InitializationSegment

  • For audio: Streams(default-audio.cmfa)/InitializationSegment

Media segments: naming

Media segments after the initialization segment must following this naming pattern:

Streams default-<type>.<ext>/Segment(<sequence-number>)

Where:

<type> is video or audio

<ext> is cmfv or cmfa

<sequence-number> must increase monotonically, although it doesn't have to be contiguous. Each sequence number must match the sequence number in the MovieFragmentHeader box.

For example:

Streams default-video.cmfv/Segment(<sequence-number>)

End of Stream indicator

The last media segment in the session must be:

  • A media segment with the lmsg brand included in the compatible brands under the SegmentTypeBox.

If you can't signal the end of stream in this way, there is a workaround. See Step C: Deliver the source media.

Example

The following code shows how to use FFMPG to format the media to follow these requirements. The commands demux, segment, and containerize the video and audio. Note the -init_seg_name and -media_seg_name lines

$ mkdir 'Streams(default-video.cmfv)'
$ ffmpeg -i input.mp4 \
-map 0:v:0 -c:v libx264 \
    -profile:v main -pix_fmt yuv420p \
    -g 30 -keyint_min 30 -sc_threshold 0 \
    -force_key_frames 'expr:gte(t,n_forced*1)' \
    -f dash -seg_duration 1 -use_timeline 0 \
    -use_template 1 -remove_at_exit 0  \
    -init_seg_name 'Streams(default-video.cmfv)/InitializationSegment' \
    -media_seg_name 'Streams(default-video.cmfv)/Segment($Number%09d$)' \
    'video.mpd'

$ mkdir 'Streams(default-audio.cmfa)'$ ffmpeg -i input.mp4 \
    -map 0:a:0 -c:a aac -ar 48000 -ac 2 \
    -f dash -seg_duration 1 -use_timeline 0 \
    -use_template 1 -remove_at_exit 0 \
    -init_seg_name 'Streams(default-audio.cmfa)/InitializationSegment' \
    -media_seg_name 'Streams(default-audio.cmfa)/Segment($Number%09d$)' \
    'audio.mpd'