Author Topic: Pixellated videos  (Read 183 times)

oscarodas

  • Newbie
  • *
  • Posts: 15
Pixellated videos
« on: October 09, 2019, 04:00:45 AM »
Hi, I'm using Avidemux 7.4 on os x 10.15 Catalina, when I trim a video and save it; I can see exactly where I did the cut because the video gets pixellated in the edited section, so if I make five cuts the video plays smoothly and becomes pixallated on the beginning of the different cuts. the Default postprocessing has all the option on at Strength :2, that was chosen automatically when I installed Avidemux, is there any other filter I should enable or disable? Thank you.
Oscar

eumagga0x2a

  • Moderator
  • Hero Member
  • *****
  • Posts: 3302
Re: Pixellated videos
« Reply #1 on: October 09, 2019, 04:37:31 AM »
Default postprocessing settings are compeletely irrelevant.

I assume you cut in copy mode. Artifacts at cut points occur if the cuts are not on keyframes.

It is more complicated with HEVC streams, the necessary checks are not yet implemented, but even there cuts should be placed always on keyframes.

oscarodas

  • Newbie
  • *
  • Posts: 15
Re: Pixellated videos
« Reply #2 on: October 09, 2019, 07:34:33 AM »
Yes, I cut in Copy mode but always use the mouse with the Go to next key frame button.Doing that I get : Frame type: I-FRM ( ).
I will try to cut using  HEVC (x265) as video output and see the results.

oscarodas

  • Newbie
  • *
  • Posts: 15
Re: Pixellated videos
« Reply #3 on: October 09, 2019, 07:58:29 AM »
You are right, saving the file to HEVC (x265), or Mpeg4 ASP (x264) work ok, but there is a big downside the original file is 46mb, the saved files are 106, and 120mb and takes 8 minutes first instance and two minutes the second option. I guess I will give up because I hoped to trim some tv series but that would fill my hard drive.

eumagga0x2a

  • Moderator
  • Hero Member
  • *****
  • Posts: 3302
Re: Pixellated videos
« Reply #4 on: October 09, 2019, 01:20:09 PM »
Yes, I cut in Copy mode but always use the mouse with the Go to next key frame button.Doing that I get : Frame type: I-FRM ( ).

Then you should not get any artifacts at cut points (using up and down keys is much more efficient than using mouse however). The only known situation which can result in artifacts despite cuts being on keyframes are source videos encoded using the HEVC codec.

Quote
I will try to cut using  HEVC (x265) as video output and see the results.

This is a misunderstanding, I did not recommend that. I asked you whether the source video is HEVC.

oscarodas

  • Newbie
  • *
  • Posts: 15
Re: Pixellated videos
« Reply #5 on: October 10, 2019, 01:54:14 AM »
I didn't implied that it was your suggestion, I said I will try, I found out that using mkv files encoded with the HEVC x265 codec gives the problem, tried about 20 different mkv to mp4 converters and all gave huge files as output, this morning found an old program I bought a while ago and never used is iVl 4, and is superfast and the files are always the same size or slightly smaller, the output is m4v, and when edited dont' pixelate, the only concern is that when saving the file Avidemux outputs them as mp4, is there any difference between the m4v and mp4 formats? Thank you.

eumagga0x2a

  • Moderator
  • Hero Member
  • *****
  • Posts: 3302
Re: Pixellated videos
« Reply #6 on: October 10, 2019, 02:26:13 PM »
I found out that using mkv files encoded with the HEVC x265 codec gives the problem

Yes, this is a known issue with some HEVC streams. Do you experience pixelated pictures at cut points (i.e. missing reference frames) also when playing a HEVC stream cut in copy mode with QuickTime? Or is it limited to Avidemux itself and other FFpeg-based software like VLC?

Quote
tried about 20 different mkv to mp4 converters

You mix up unrelated things – container and codec. Both MKV and MP4 are fully suitable for a HEVC stream. HEVC provides a very good compression rate, clearly superior to the older H.264. To keep file size approximately the same (which means to keep the bitrate as low as with HEVC despite much lower efficiency) when re-encoding to H.264, you need to accept a very substantial quality loss.

A valid reason to re-encode HEVC into H.264 is missing hardware decoding support due to old hardware, otherwise I would recommend to stick to HEVC.

is there any difference between the m4v and mp4 formats?

No. Both are naming conventions for one and the same MPEG-4 Part 14 format.

oscarodas

  • Newbie
  • *
  • Posts: 15
Re: Pixellated videos
« Reply #7 on: October 12, 2019, 07:01:58 PM »
 What was the source of these input videos? Avidemux? Most of my videos are downloaded from the net.I have encoded them using Vidconvert Codec:H265
Today I tried different videos using different formats and when I choose save in copy mode they get pixellated, but if I choose save: HEVC (x265)they are ok. so the lesson is that I have to be patient and use HEVC instead of copy.
I'm writing from the Safari Browser, the last one I used was Microsoft Edge for mac (Beta)

eumagga0x2a

  • Moderator
  • Hero Member
  • *****
  • Posts: 3302
Re: Pixellated videos
« Reply #8 on: October 12, 2019, 11:25:46 PM »
I have encoded them using Vidconvert Codec:H265

This means that the source of the videos was VidConvert.

Quote
Today I tried different videos using different formats

Formats or codecs?

Quote
and when I choose save in copy mode

With all cut points placed on keyframes?

Quote
they get pixellated,

Despite cuts on keyframes and "sanitize timestamps" set to off?

Quote
but if I choose save: HEVC (x265)they are ok.

This is obvious as the whole stream is regenerated.

Quote
so the lesson is that I have to be patient and use HEVC instead of copy.

A better choice whould be to provide a sample with exact steps to reproduce these bad cuts in order to get the issue fixed if possible.

oscarodas

  • Newbie
  • *
  • Posts: 15
Re: Pixellated videos
« Reply #9 on: October 13, 2019, 01:06:18 AM »
Hi, today I did some testing with a file Video output HEVC and on the configure panel tried the constant Bitrate, Constant Quantiser, and Constant Rate Factor, all three files to me seem the same in quality but found out that the Constant Rate Factor is almost 1/3 the size of the other two, so I have saved those settings as default, also all three settings take the same time when saving.  As for your questions.
1- Source VidConvert
2- Formats or Codecs I tried HECV, output mkv and mp4 and H264 output mkv and mp4.
3- Yes all cuts are on keyframes, I always use the arrow keys, even the mouse does the trick when pressing the button    forward, it says Go to next keyframe if I rest the mouse on top of it.
4- The Sanitize timestamps are set to off.
As I explained above I'm happy to set the Video Output to HEVC (x265) Constant Rate Factor (Single Pass).
Doing that I haven't had one single damaged file. Thanks again.