вс, 8 июн. 2025 г., 18:26 Terje J. Hanssen via Cin <cin@lists.cinelerra-gg.org>:

Den 06.06.2025 14:17, skrev Terje J. Hanssen:

While the newer h.264 and hevc are known for best compression, mpeg2 may have better quality at video bitrate > 30Mbps

This example capture a raw video stream (optional tape playback) from the camera sensor over HDMI out and transcode audio to PCM into a high-end mpeg2hd422p.m2ts
-input_format yuyv422 -video_size hd1080 possibly may be commented out, as the encoder default uses the maximum capability it get from the capture card ms2130 and driver v4l2

mpeg2video is difficult to get quit perfect with ffmpeg; muxing overhead: 6.206455% is the minimum I have achieved as in this case.

At this high bitrate, 39Mbps here, a combination with segmented recording is suggested and preferred to control the file sizes (segments) and eventually corrupted parts better.


ffmpeg -hide_banner -f v4l2 -framerate 50 -i /dev/video0 -f alsa -ac 2 -i hw:CARD=UHD,DEV=0 -c:v mpeg2video -refs 1 -bf 2 -b:v 35M -maxrate 35M -minrate 35M -bufsize 38M -muxrate 38M -dc 10 -c:a pcm_bluray -mpegts_m2ts_mode 1 -t 30 -f mpegts mpeg2hd422p_35M.m2ts

Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 79.422429, bitrate: 1658880 kb/s
  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1920x1080, 1658880 kb/s, 50 fps, 50 tbr, 1000k tbn
[aist#1:0/pcm_s16le @ 0x55e2664e95c0] Guessed Channel Layout: stereo
Input #1, alsa, from 'hw:CARD=UHD,DEV=0':
  Duration: N/A, start: 1749208971.359170, bitrate: 1536 kb/s
  Stream #1:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> mpeg2video (native))
  Stream #1:0 -> #0:1 (pcm_s16le (native) -> pcm_bluray (native))
Press [q] to stop, [?] for help
[mpeg2video @ 0x55e2664d0500] Warning vbv_delay will be set to 0xFFFF (=VBR) as the specified vbv buffer is too large for the given bitrate!

Output #0, mpegts, to 'mpeg2hd422p_35M.m2ts':
  Metadata:
    encoder         : Lavf61.7.100
  Stream #0:0: Video: mpeg2video (4:2:2), yuv422p(tv, progressive), 1920x1080, q=2-31, 35000 kb/s, 50 fps, 90k tbn
      Metadata:
        encoder         : Lavc61.19.101 mpeg2video
      Side data:
        cpb: bitrate max/min/avg: 35000000/35000000/35000000 buffer size: 38000000 vbv_delay: N/A
  Stream #0:1: Audio: pcm_bluray, 48000 Hz, stereo, s16, 128 kb/s
      Metadata:
        encoder         : Lavc61.19.101 pcm_bluray
[out#0/mpegts @ 0x55e2664e9740] video:128445KiB audio:5648KiB subtitle:0KiB other streams:0KiB global headers:0KiB muxing overhead: 6.206455%

frame= 1500 fps= 50 q=3.5 Lsize=  142416KiB time=00:00:29.98 bitrate=38915.0kbits/s speed=0.998x

I have been able to tune the ffmpeg specifications further:

• '-profile:v 422p -level:v high' (for mpeg-2 profile 422P@HL)
• '--ch_layout stereo' (as a replacement for  '-ac 2' that caused 'Guessed Channel Layout: stereo')

And also verified the camera HDMI out 'raw video' and 'raw audio' (pcm) using just the ffmpeg input parts:

ffmpeg -hide_banner -f v4l2 -framerate 50 -i /dev/video0 -f alsa -ch_layout stereo -i hw:CARD=UHD,DEV=0

Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 191.096360, bitrate: 1658880 kb/s
  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1920x1080, 1658880 kb/s, 50 fps, 50 tbr, 1000k tbn
Input #1, alsa, from 'hw:CARD=UHD,DEV=0':
  Duration: N/A, start: 1749375770.007003, bitrate: 1536 kb/s
  Stream #1:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s


Attached here  is a full ffmpeg debug log file for verification (command below)

• mpeg2hd422p_35M.log.gz

ffmpeg -loglevel debug -f v4l2 -framerate 50 -i /dev/video0 -f alsa -ch_layout stereo -i hw:CARD=UHD,DEV=0 -c:v mpeg2video -profile:v 422p -level:v high -refs 1 -bf 2 -b:v 35M -maxrate 35M -minrate 35M -bufsize 38M -muxrate 38M -dc 10 -c:a pcm_bluray -mpegts_m2ts_mode 1 -t 30 -f mpegts mpeg2hd422p_35M.m2ts > mpeg2hd422p_35M.log 2>&1

-----------

Among CinGG's existing m2ts presets

cd /Leap_root/usr/share/cin/ffmpeg/video

ls -1 *m2ts

• avc422.m2ts
• bluray_bff.m2ts
• bluray_dv_ntsc.m2ts
• bluray_dv_pal.m2ts
• bluray_fakeinterlace.m2ts
• bluray_lo.m2ts
• bluray.m2ts
• bluray_tff.m2ts
• hevc422p10.m2ts
• hevc422p8.m2ts
• lossless.m2ts
• visually_lossless.m2ts

grep mpeg2video *m2ts

• That is none so far for mpeg2video HD and 422p

If this preset can be specified and supplemented (?) for use with pcm_bluray and segmented recording, I can test it next ;)

I think you can copy existing mpeg2 m2ts  preset with different, desired name  (in same folder where other presets reside)

and just add you parameters there?

or try to put text below in new profile ....

mpegts mpeg2video

cin_pix_fmt=yuv422p

b=35M

dc=10

muxrate=38M

minrate=35M

maxrate=35M

bufsize=38M

bf=2

profile=high

refs=1