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Video Scripts

  1. Create Reference Encoding
  2. Extract I-Frame Positions
  3. Generate VBR Job Files
  4. Generate CBR Job Files

Create Reference Encoding

Create reference encodings manually or by using

python createVars.py [input] [fps] [maxmimum-durations]

Specify for [maxmimum-durations] a list for the maximum segment duration lengths, i.e. 4,6,8,10.

Extract I-Frame Positions

Extract the timestamps of the I-frame positions by using

python getTimeStamps.py [input m3u8] [fps] [sub]

Enable substraction of 1/4 frame duration by replacing [sub] with true. We use FFmpeg to extract the "best-effort-timestamps" of all I-frames that are at the beginning of a segment. To cope with floating point imprecision we subtract a small safety margin (1/4 frame duration). This ensures that the next frame after the adjusted timestamp is the frame which shall be encoded as I-frame. When using force key frame with this timestamp the next frame will be encoded as key frame.

Generate VBR Job Files

Add the extracted I-frame timelines to the dictionary [Bunny/Elfuente/Meridia/TearsOfSteel]_t_sub in generateJobs.py. Ignore the dictionaries with the exact timestamps. It should follow this style:

Max Duration Timeline
4 "0.0,3.98958,4.40625,8.40625,..."
6 "0.0,4.19791,10.19791,16.19791,..."
8 "0.0,4.19791,12.19791,16.28125,..."
10 "0.0,4.19791,14.19791,16.28125,..."

Add the maximum segment duration for all variable-length encodings in generateJobs.py.

For the next step, you need to have the extracted average segment lengths of the variable-length encodings and round them to a precision of 0.5s. You can do this by first creating the variable-length encodings jobs python generateJobs.py and use the video docker to create the encodings and the video statistics files. Afterward, you can use

grep -oP '"durations_mean":\s(\d+\.\d+)' video_statistics.json

to extract the average segment length of the corresponding encoding. If you did this, you can remove the durations for variable lengths from generateJobs.py, otherwise, you will create those job files again in the next step.

Add the corresponding average lengths and the maximum lengths for the fixed lengths encodings in generateJobs.py. In the end, you can run

python generateJobs.py

to create all variable bitrate jobs.

Add the job files to the working queue of the docker container and start the encoding process.

Generate CBR Job Files

Use

python extractCBRStats.py [DIR] [OUTPUT]

to extract needed bitrate information. The [DIR] input parameter should point to the result directory of the VBR Jobs. The [OUTPUT] parameter should specify the output of the program as a JSON file, e.g. cbr_jobs.json.

Use

python generateJobs.py cbr_jobs.json

to generate all constant bitrate encoding job files.