"--nativedeinterlace" has chroma upsampling error/artifacts for interlaced SD 4:2:0 mpeg2/h264/dv footage in high motion/saturated Red/Blue/Green on dark contrasts + workaround

Very recently the following Rpi firmware fix has been committed for improved usage of the hardware advanced deinterlacer eliminating artifacts in heavy saturated green color motion in interlaced SD 4:2:0 footage:

firmware: di_adv: Fix for green artifacts regression https://github.com/raspberrypi/firmware/commit/debe2d29bbc3df84f74672fae47f3a52fd0d40f1

Although the focus for my issue is not deinterlacing with "progressive output" but using --nativedeinterlace with "interlaced output" which is contrary to this recent firmware fix, I think they might share the same root cause which is called Chroma Upsampling Error which is prominent on interlaced 4:2:0 SD material with high saturation and motion especially in Red/Blue/Green & Orange on dark contrast areas. This recent mentioned firmware fix doesn't cause (as in regression) nor fixes the issue reported here!

Problem: SD interlaced 4:2:0 mpeg2/h264/dv video content files and or (live) streams is playedback using omxplayer on the HDMI output of the Rpi in its corresponding footage format/resolution.

omxplayer intro-clean.m2v --nativedeinterlace -I -s --loop
Input #0, matroska,webm, from 'intro-mjpeg.mkv':
  Metadata:
    ENCODER         : Lavf56.40.101
  Duration: 00:00:08.28, start: 0.040000, bitrate: 12996 kb/s
    Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 720x576 [SAR 16:15 DAR 4:3], 25 fps, 25 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      ENCODER         : Lavc56.60.100 mjpeg
      DURATION        : 00:00:08.280000000
Output mode 21: 720x576@50 NI:15
ntsc_freq:0 
Video codec omx-mjpeg width 720 height 576 profile -99 fps 25.000000
Subtitle count: 0, state: off, index: 1, delay: 0
Error: Unable to open font0k/  4800k A:  0.00   0.00s/  0.00s Cv:     0k Ca:     0k                            
V:PortSettingsChanged: 720x576@25.00 interlace:0 deinterlace:0 anaglyph:0 par:1.00 display:0 layer:0 alpha:255 aspectMode:0
Seek to: 00:00:0006s      0k/  4800k A: -8.14   0.00s/  0.00s Cv:     0k Ca:     0k

Using Rpi 720x576i PAL mode21/22, disable overscan, hdmi_pixel_encoding=3/4 using pixelformat 422 and 4/3 16/9 aspectratios shows Chroma Upsampling Error artifacts as in shown/recorded in this picture Red on Black contrasts. Left is correct upsampled/scaled interlace aware chroma upsampling 4:2:0 to 4:2:2 and right is incorrect. Left uses MJPEG422 as codec and right any other 4:2:0 interlaced supported codec like mpeg2/h264.

chroma-error-capture

Since real interlaced output using odd/even synced fields is possible on the Rpi since "vcgencmd hvs_update_fields X" commit: https://github.com/raspberrypi/firmware/issues/292 The only thing that Rpi is missing is interlaced aware chroma 420 upsampling 422 for interlaced SD HDMI output done by gpu/firmware?

Sample footage: The same SD 16/9 PAL 4:2:0 interlaced h264 footage from the following kodi topic can be used "Swiat wedlug Kiepskich - odc. 351.ts": http://forum.kodi.tv/showthread.php?tid=304573&pid=2505220#pid2505220

This is my test footage "intro-clean.m2v" SD 4/3 PAL 4:2:0 mpeg2 upperfield interlaced footage: https://github.com/mltframework/mlt/files/737768/intro-clean.m2v.zip https://we.tl/domVSVxnC3

Workaround: The only 4:2:2 footage the Rpi can play natively through omxplayer is MJPEG codec (correct me if I'm wrong). Other 4:2:2 capable codecs like Apple Prores, Avid DNxHD, MPEG2 IMX, XDCAM, raw yuv422 are only playable by CPU Rpi2/3 and VLC/KODI, but than I have no control over the interlacing/field sync.

Preconverting your 4:2:0 interlaced SD footage mpeg2/h264/dv to MJPEG (422 interlaced) with ffmpeg/avconv is a workaround for video files / offline only content. Using the "-vf scale=interl=1" flag makes ffmpeg aware of interlaced chroma upscaling to its output color pixel format!

ffmpeg -i intro-clean.m2v -vf scale=interl=1 -vcodec mjpeg -qscale 2 -pix_fmt yuvj422p -f matroska intro-clean-mjpeg.mkv

This will play correct with no chroma upsample artifacts. omxplayer intro-clean-mjpeg.mkv --nativedeinterlace -I -s --loop

For live TV/streaming content the only fix would be in Rpi firmware.

Hardware: Rpi 2 Blackmagic Intensity 4K hdmi in / component out to CRT monitor Sony PVM-20m4e CRT interlaced High Resolution broadcast monitor

Software: Raspbian GNU/Linux 8.0 (jessie) Linux raspberrypi 4.4.45-v7+ #954 SMP Fri Jan 27 19:06:40 GMT 2017 armv7l GNU/Linux omxplayer - Commandline multimedia player for the Raspberry Pi Build date: Thu, 19 Jan 2017 23:25:26 +0000 Version : 12b472e [master] Repository: https://github.com/popcornmix/omxplayer.git

Config.txt: disable_overscan=1 hdmi_force_mode=1 hdmi_pixel_encoding=3 hdmi_drive=2 hdmi_group=1 hdmi_mode=21 decode_MPG2=using validcode gpu_mem=256 max_usb_current=1

Background Info Similar Problem/Workaround: Professional broadcast SDI/HDMI video signal playback hardware (blackmagic Decklink/Intensity) show the exact same Color artifacts as the Rpi when outputting the same 4:2:0 footage on these SDI and HDMI a 4:2:2/4:4:4 devices using similar ffmpeg based broadcast software solutions like MLT-framework & CasparCG. The same workaround applies and have been committed this week to the github!

https://github.com/mltframework/mlt/issues/172 ##fixed in 2.2.0

https://github.com/CasparCG/Server/issues/41 ##fixed in 6.6.0

The following article is detailed, only take a look at the pictures if reading takes to much time: http://web.archive.org/web/20060719025947/http://www.hometheaterhifi.com/volume_8_2/dvd-benchmark-special-report-chroma-bug-4-2001.html

popcornmix / omxplayer

"--nativedeinterlace" has chroma upsampling error/artifacts for interlaced SD 4:2:0 mpeg2/h264/dv footage in high motion/saturated Red/Blue/Green on dark contrasts + workaround #522