[wip] Lossless hdr

[mollyxu]

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[pytorch-bot]

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❌ 2 New Failures

As of commit 230896a with merge base bdccc0b ():

NEW FAILURES - The following jobs have failed:

• Build and test Linux wheel / install-and-test-third-party-interface (3.10, 8.0) (gh)
  /home/runner/work/torchcodec/torchcodec/test/third-party-interface/ThirdPartyInterfaceTest.cpp:37:5: error: could not convert ‘<lambda closure object>facebook::torchcodec::{anonymous}::<lambda(const facebook::torchcodec::StableDevice&)>()’ from ‘facebook::torchcodec::{anonymous}::<lambda(const facebook::torchcodec::StableDevice&)>’ to ‘facebook::torchcodec::CreateDeviceInterfaceFn’ {aka ‘std::function<facebook::torchcodec::DeviceInterface*(const torch::stable::Device&)>’}
• Build and test Windows wheel / install-and-test (3.10, 4.4.2) (gh)
  test/test_decoders.py::TestVideoDecoder::test_10bit_float32_against_ffmpeg_rgb48[approximate-asset2-cpu]

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[s-deeper]

Small correctness concern in the new P016 path:

convertP016FrameToRGB() always falls back to bt601LimitedRange16ColorTwist for non-BT.709 / non-BT.2020 content. The 8-bit path doesnt do that: when colorspace is unspecified, it still branches on color_range and uses BT.601 full-range for AVCOL_RANGE_JPEG.

Should the 16-bit fallback mirror that behavior? As written, a >8-bit full-range or partially tagged source could be silently decoded as limited-range.