Interlace detection and deinterlace option

[double-u-a]

Describe the problem to be solved

A lot of source videos are interlaced, including older videos and 1080i broadcast footage. These will have interlace artifacts as Peertube's upload encoding assumes a progressive input. Having to deinterlace videos before uploading adds an unnecessary double encoding which reduces the quality of the video.

Describe the solution you would like

Add an option to detect interlacing (through ffmpeg idet tool) and then if an uploaded video is interlaced, add an option to deinterlace using yadif/bwdif as a filter for the peertube encoding stage.

[Chocobozzz]

Hi,

Can you provide ffmpeg commands to detect and deinterlace videos?

[double-u-a]

Sure here is what I do in Python at the moment before uploading to Peertube

This is the detection function I use using ffmpeg's idet filter:

def deinterlace_checker(filepath):
    cmd = f'ffmpeg -i "{filepath}" -filter:v idet -frames:v 2 -an -f null -'
    ffmpeg_output = subprocess.run(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    output_str = str(ffmpeg_output)

    if "Single frame detection: TFF" in output_str or "Single frame detection: BFF" in output_str:
        print('Interlaced: YES')
        return True
    else:
        print('Interlaced: NO')
        return False

Then the ffmpeg encoding logic using the function to detect (note I am using a yadif config which interpolates the frames and turns e.g. 1080i50 into 1080p50, a standard yadif=1 filter would turn 1080i50 into 1080p25.

if deinterlace_checker(file.filepath) == True:
        command = f'ffmpeg -y -i "{file.filepath}" -vf "yadif=mode=send_field:parity=auto:deint=all" -r "{2* file.fps_round}" -c:a aac "{outpath}"'
        print('Deinterlacing to temp:', command)
        response = subprocess.call(command, shell=True)
        print(response)
        uploadfile = outpath
    else:
        uploadfile = file.filepath