added yuvj420p format for to_ndarray

[mastak]

yuvj420p has the same shape as yuv420p. The difference in color ranges:

• yuv420p according to rec 709 (https://en.wikipedia.org/wiki/Rec._709#Digital_representation) has a nominal range of [16..235] for Y channel and CB and CR channels have a nominal range of [16..240]. rec 601 has limited ranges also. It's main recommendations for yuv420p (https://en.wikipedia.org/wiki/YUV)

• yuvj420p like I420, but with a full range ("digital", 0-255) (https://wiki.videolan.org/YUV#J420)

[mastak]

Script with comparing pyav vs native ffmpeg run as subprocess:

requirements:

Install imageio-ffmpeg, for run ffmpeg as a subprocess and read raw data (https://github.com/imageio/imageio-ffmpeg/blob/master/imageio_ffmpeg/_io.py#L63)

pip install git+https://github.com/imageio/imageio-ffmpeg.git@53b1533382ec6502e2e02a3640898603a03fc00f

import av
import numpy as np
from imageio_ffmpeg import read_frames
from av.datasets import fate


def av_arrays(path_):
    return [frame.to_ndarray(format='yuvj420p') for frame in av.open(path_).decode(video=0)]


def ffmpeg_arrays(path_):
    gen = read_frames(path=path_, pix_fmt='yuvj420p', bits_per_pixel=12)
    meta = next(gen)
    data = list(gen)
    yuv = np.frombuffer(b''.join(data), dtype='uint8')
    w, h = meta['size']
    return yuv.reshape(-1, int(h * 1.5), w)

path = fate('h264/interlaced_crop.mp4')
av_frames = av_arrays(path)
ffmpeg_frames = ffmpeg_arrays(path)

for av_frame, ffmpeg_frame in zip(av_frames, ffmpeg_frames):
    assert np.array_equal(av_frame, ffmpeg_frame)

[jlaine]

This looks good to me, let's go!