The long play analysis (formerly also known as live mode) is a metadata analysis function of Cm_analyze (part of the Dolby Vision Professional Tools) and 3rd party tools supporting this feature that automatically analyzes and creates dynamic metadata on a frame-by-frame basis from PQ (HDR10) encoded sources to deliver content in Dolby Vision.

 

Cm_analyze

The Cm_analyze tool is used to convert existing ST.2084 encoded (PQ/HDR10) content to Dolby Vision by automatically generating dynamic Dolby Vision metadata. The metadata can either be generated shot-by-shot when using a shot list or frame-by-frame when using the long play analysis mode. The generated metadata and the PQ source are then used to create a Dolby Vision Mezzanine or Dolby Vision Master deliverable to be encoded and distributed.

Required information and files for shot based metadata analysis

In order to analyze shot-by-shot metadata, the following assets are required:

• Conformed HDR image sequence that is encoded in SMPTE ST.2084 (PQ)
• Shot list with shot type for the entire sequence (.txt, .sl, .edl).
• Aspect ratios for the sequence
• Source format
• Mastering Display
• Frame Rate

 

Required information and files for frame-by-frame metadata analysis - long play analysis

In order to analyze frame-by-frame metadata the, following assets are required:

• Conformed HDR image sequence that is encoded in SMPTE ST.2084 (PQ)
• Aspect ratios for the sequence
• Source format
• Mastering Display
• Frame Rate

Using shot-based analysis

Shot-based analysis is used when there is an existing shot list or EDL for the PQ/HDR10 deliverable that is to be converted for a Dolby Vision delivery. In shot-based analysis mode (default), Cm_analyze creates shot-by-shot dynamic metadata. Cm_analyze will analyze every frame of the asset and conform metadata into shots based on the shot list.
The resulting XML will contain multiple shots with dynamic metadata for the entire sequence.
By default, the shot-based analysis will apply CMv4 analysis and output a v4.0.2 XML.

Example of shot-based analysis usage with a ProRes 422 source:

./cm_analyze -s <shotlist.txt> --source-format "u10 i422 lsb32rev le ycbcr_bt2020 pq bt2020 video" --aspect-ratios 1.77778 2.4 --mastering-display 21 -- frame-rate 24000/1001 <input_prores_422.mov> <output.xml>
 

Using long play analysis

Long play analysis is used when there is no shot list or EDL for the PQ/HDR10 deliverable that is to be converted for a Dolby Vision delivery. In long play analysis, Cm_analyze creates frame-by-frame dynamic metadata. Using "--longplay-analysis" with Cm_analyze, the tool will analyze every frame of the asset and apply a temporal filter between frames to smooth transitions between cuts or abrupt transitions.
The resulting XML will contain a single shot with per-frame dynamic metadata for the entire sequence.
By default, long play analysis will apply CMv4 analysis and output a v4.0.2 XML. This is the recommended mode to create per-frame metadata.

Example of longplay analysis usage with a ProRes 422 source:

./cm_analyze --source-format "u10 i422 lsb32rev le ycbcr_bt2020 pq bt2020 video" --aspect-ratios 1.77778 2.4 --mastering-display 21 --frame-rate 24000/1001 <input_prores_422.mov> <output.xml> --longplay-analysis
 

 

Review of auto-generated metadata

The Dolby Vision deliverable generated by Cm_analyze can be reviewed using content mapping. You can either use a Dolby Vision enabled Color Grading or Mastering Tool with either an internal (iCMU) or external (eCMU) to review the mapped versions. Alternatively, use Cm_offline to render a mapped version using the dynamic metadata for tone mapping.

More info on how to use the long play analysis can be found in the Dolby Vision Professional Tools User Manual