Guide on how to create DASH on-demand content

python/content_production/how_create_dash_ondemand.md

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+## How to make DASH OnDemand content following DASH-IF IOP spec.
+
+Goal:
+
+* Create content in DASH OnDemand profile using SegmentBase. This uses sidx to describe all the segments in the tracks. Follows DASH-IF IOP.
+* Audio segments that don't drift with respect to video. E.g. output from MP4Box may need to be adjusted
+
+Two tools are needed:
+
+1. `batch_encoder.py` to encode the content into the various video and audio tracks needed.
+2. `create_ondemand_dash.py` to generate MPD and CMAF tracks.
+
+To get PYTHON paths to work properly, run the scripts from the directory `batch_ffmpeg`.
+
+Normal chain:
+
+Generating MP4 track files.
+
+* Start with mp4 file for content.
+* Write JSON config file with correct video settings and audio settings for `batch_encoder.py`
+* Run `batch_encoder.py` which will generate one file per video and audio track (e.g. V1200.mp4, V2400.mp4, A96_eng.mp4)
+* All the different tracks are in the same directory, which is what the next step takes as input
+
+Generate DASH OnDemand content from MP4 track files
+
+* Here we use the tool `create_ondemand_dash.py`
+* It takes the parameters: cfg_file.json, directory where the MP4 tracks are
+* the cfg_file.json lists the video and audio tracks and tells the duration in milliseconds of the segments
+* the tool runs MP4Box to generate DASH media tracks and manifest. It then runs a tool to fix the audio segment durations inplace
+
+
+### Limitations
+
+* Subtitles are currently not handled. They need to be added by hand by modifying the output MPD. This will be fixed in a later version.
+