Enable color parameters in NVENC test on FFmpeg 4 and 6

[Dan-Flores]

Investigate why FFmpeg 4 and 6 fail with non-default color space and range.
The test_nvenc_against_ffmpeg_cli test is currently skipped on FFmpeg 4 and FFmpeg 6 when colorspace and color_range are set to values besides the default BT.601 and tv .

The code below demonstrates that the color parameters are set on the codec context, and the encoded video has the correct metadata. The error may be caused by other steps in the test.

Details

import subprocess
import torch
import json
from torchcodec.encoders import VideoEncoder

# Create test frames and encode with specific color parameters
frames = torch.randint(0, 256, (5, 3, 256, 256), dtype=torch.uint8).to("cuda")
encoder = VideoEncoder(frames=frames, frame_rate=30)

encoder.to_file(
    dest="/tmp/test_video.mp4",
    codec="h264_nvenc",
    extra_options={
        "colorspace": "bt709",
        "color_range": "pc",
    }
)

result = subprocess.run(
        [
          "ffprobe",
          "-v",
          "error",
          "-select_streams",
          "v:0",
          "-show_entries",
          "stream=color_space,color_range,pix_fmt",
          "-of",
          "json",
          "/tmp/test_video.mp4"
        ],
        capture_output = True,
        text = True,
        check = True)

metadata = json.loads(result.stdout)["streams"][0]
print(json.dumps(metadata, indent=2))