[2.6.15] Inconstant video size

[glop]

Hello,

I have Avidemux 2.6.15 on Lubuntu and, since some versions, I have a problem with video size.
I must double video size for, with lucky, get my video with the good size.

Yesterday, I reencode video, with "1600 MB" in video codec parameter, and I has got a file a bit more 800 MB => it's OK !
Today, I reencode an another video with same parameters : file size = ~1600 MB

I use MPEG-4 AVC (x264) for video, copy for audio, in MKV muxer.

Thanks for your help !

[Jan Gruuthuse]

If these are not the same kind of video, could be normal.
If the video has the same resolution, frames and duration the difference should not be so big.
Like 720p 50 frames 38 seconds duration?

The test done: Source video: 68.8 MB (3sat video 720p)
Video Size (Two Pass)
Target Video Size: 28 MB
The end result was 37 MB instead of the wanted 28 MB.

It is always an estimation and is trying to do so.
Image content could be a big thing to:
- Steady imagery with less movement result in smaller sized video.
- Action film with fast moving different imagery would result in bigger sized video.

[glop]

Same resolution, same format.

1080p, between 1h30 and 2h00 of duration (record video TV ), 25 fps (50 fps isn't supported by my tv recorder).
Video codec is in AVC (MPEG 4 ?)
Audio codec (for french track only) : generaly equal or superior at 128 Kpbs, AC3 / E-AC3 / sometimes in MP3 (rare).

I didn't have this problem before update in 2.6, but this version is require (record in .mts, not supported on 2.5).

[Jan Gruuthuse]

same channel and content?

[glop]

Same channel and same type of content (for my 2 tests : Taken and Taken 2, 2 movies with rapid movement).

EDIT : In any case, nothing justify the size difference.

[Jan Gruuthuse]

Check with MediaInfo both source video for Video bitrate
example:

1) 20161128 1400 - SWR BW HD
Video Bit rate                                 : 12.6 Mbps

2) 20161223 1400 - SWR BW HD
Video Bit rate                                 : 12.2 Mbps

that could explain some 0.4 Mbps difference/second, same series.

use the latest (24/12/2016) for your OS: http://www.avidemux.org/nightly/

[glop]

Average bitrate is 4378 Kbps (2 movies and advertisements in only 1 file).
I have again 2 movies to reencode (2 differents files), I will check result.

[Jan Gruuthuse]

I'm not certain about this:
With MPEG-4 AVC (x264) and your cpu is doing other stuff also (high load) if this will influence the end result.
Less calculations are made resulting in larger video code?
Developers could time permitting perhaps provide more info on this.

you got PM

[mean]

IF the Qz is at its minimum it's normal

[glop]

Qz ? How I can see Qz value ?

[mean]

When you load your video, check the number beside the frame type
i.e.
I(2) <= Qz=2
In generla 2 is the minimum = highest quality

[glop]

Hello,

I think have found the bug, with target size to 800M :

• First try : file < 500 MB
• Second try : 882 MB. Difference ? I have applied FPS filter ("change FPS"), with "source 25 - dest 25" as setting

Tested with 2.6.18.

[Jan Gruuthuse]

If the video is using variable frame rate and you are forcing somehow to use 25fps (non variable frame rate), this could explain the issue. New Frames are created?

[glop]

No idea, but the original video is in 25 FPS. It is only when I apply the FPS filter that the size of the reencoded video is equal to the size shown.

Without filter, my video size is divided by 2.