Estimated reading time: 4 minutes

 

Summary

Long play analysis is a frame-by-frame metadata analysis mode in CM Analyze (part of the Dolby Vision Professional Tools) and supported third-party tools. It automatically generates dynamic Dolby Vision metadata from ST.2084 (PQ) encoded sources to deliver content in Dolby Vision.

 

Who this is for

Post-production professionals, mastering engineers, and technically literate HDR users working with PQ/HDR10 content who need to convert existing material to Dolby Vision.

Background

CM Analyze converts existing ST.2084 (PQ/HDR10) content to Dolby Vision by automatically generating dynamic Dolby Vision metadata. Metadata can be generated in two modes:

• Shot-by-shot — requires a shot list or EDL
• Frame-by-frame — uses long play analysis; no shot list required

The generated metadata and the PQ source are then used to create a Dolby Vision Mezzanine or Dolby Vision Master deliverable for encoding and distribution.

 

Analysis modes

Shot-based analysis

Use shot-based analysis when a shot list or EDL exists for the PQ/HDR10 deliverable being converted for Dolby Vision delivery.

In this mode, CM Analyze:

• Analyses every frame of the asset
• Conforms metadata into shots based on the provided shot list
• Outputs an XML containing multiple shots with dynamic metadata for the entire sequence
• Applies CM 4.0 analysis by default and outputs a v4.0.2 XML

Required inputs:

• Conformed HDR image sequence or video file encoded in 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

Example — shot-based analysis 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>

 

 

Long play analysis

Use long play analysis when no shot list or EDL exists for the PQ/HDR10 deliverable being converted for Dolby Vision delivery.

In this mode, CM Analyze:

• Analyses every frame of the asset
• Applies a temporal filter between frames to smooth transitions across cuts or abrupt transitions
• Outputs an XML containing a single shot with per-frame dynamic metadata for the entire sequence
• Applies CM 4.0 analysis by default and outputs a v4.0.2 XML

Note: Long play analysis is the recommended mode for creating per-frame metadata.

 

Required inputs:

• Conformed HDR image sequence mor video file encoded in ST.2084 (PQ)
• Aspect ratios for the sequence
• Source format
• Mastering display
• Frame rate

No shot list is required for long play analysis.

 

Example — long play analysis 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

 

Important: In CM Analyze versions prior to v5.2, use --live-mode instead of --longplay-analysis.

 

Reviewing auto-generated metadata

Once CM Analyze has generated the Dolby Vision deliverable, review it using content mapping. Two options are available:

• Use a Dolby Vision-enabled color grading or mastering tool with an internal content mapping unit (iCMU) to review the mapped versions
• Use CM Offline to render a mapped version using the dynamic metadata for tone mapping

 

Further reading

For full usage details, refer to the Dolby Vision Professional Tools User Manual.

If you have any questions about long play analysis or CM Analyze, feel free to post them in our Dolby Vision Forum or share your findings with the Dolby Creators Community on Discord.