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Metadata for indicating maximum video bitrate in CPL #11

Open cfadamp opened 3 months ago

cfadamp commented 3 months ago

Currently, the maximum bitrate for a DCP video essence is capped at 250 Mbit/s as per RDD52 standard. However, with the increasing prevalence of high frame rate and HDR content, many DCP packages are being authored at higher bitrates of up to 400 Mbit/s or 500 Mbit/s.

Implementing this change could lead to more robust DCP handling in cinemas and other environments, e.g. creating a proper supplemental VF package with video inserts for a high bitrate package.

I propose the introduction of a new metadata field in the CPL (Composition Playlist), as defined in ST429-16, that specifies the maximum bitrate at which the DCP's jpeg2000 essences was encoded.

I welcome feedback and discussion on this proposal, or any already existing solutions that I might have missed.

jack-watts commented 2 months ago

Hey @cfadamp ,

Have you explored the option of using ExtensionMetadata?

e.g.

<ExtensionMetadata scope="http://myvendor.noname/spec/2012">
    <Name>High Frame Rate</Name> 
    <PropertyList> 
        <Property> 
            <Name>Maximum Bitrate</Name> 
            <Value>450</Value> 
        </Property> 
    </PropertyList> 
</ExtensionMetadata>

This would be a quicker win than opening up a request against ST 429-16 to include an element along the lines of MainPictureMaxBitrate.

e.g.

<MainPictureMaxBitrate units="megabit per second">450</MainPictureMaxBitrate>

Keeping it in ExtensionMetadata allows for vendors whom have implemented support for HFR playback greater flexibility in how they want to handle support for it.

You mention " more robust DCP handling..." Are you seeing challeneges with some of your HFR DCPs in cinemas?

cheers Jack