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Remove black bars feature

Well ... usually black bars use VERY little space, because the information can be described as two rectangles with one colour, which can be saved with only some bytes.
Of course it's a bit more difficult, but the size should be less than 1% of the picture size.
20% difference is a bit strange though.
 
That is of course correct. But in reality it looks different.
I have just copied a BD where the difference was significantly less at 820p. There was just a 10% saving. I have no idea where the difference comes from. I used to do the cropping afterwards with Handbrake. There were differences there too. But it definitely saves storage space.
 
cartman0208 said:
Well ... usually black bars use VERY little space, because the information can be described as two rectangles with one colour, which can be saved with only some bytes.
Of course it's a bit more difficult, but the size should be less than 1% of the picture size.
20% difference is a bit strange though.
Click to expand...

I don't read German. Is it an older film? If so, it could be caused by film grain.
 
DrXenos said:
Also, one nasty consequence of removing the black bars that I have noticed is the subtitles that would normally gone below the video, will now often times be over top of it (and if the colors clash, it can be hard to see).
Click to expand...

For me, since I project onto a maskable screen, this is a positive side effect. Otherwise the subtitles, even if not often needed, disappear in the masking and are barely legible. So they are always just above the bottom edge of the screen.
 
Barb-Wire said:
For me, since I project onto a maskable screen, this is a positive side effect. Otherwise the subtitles, even if not often needed, disappear in the masking and are barely legible. So they are always just above the bottom edge of the screen.
Click to expand...
But that would mean that the bottom part of any video without black bars (i.e., full 16:9) would also "disappear in the masking."
 
DrXenos said:
I don't read German. Is it an older film? If so, it could be caused by film grain.
Click to expand...

Garden State is from 2004.
The movie I just copied, "The Deep", is from 1977 and the savings were a good half less. Which is why I don't think it's due to age or film grain.
 
Barb-Wire said:
I am talking about spatial compression.
To get the correct aspect ratio again, I have to stretch it in the player.
That works, of course. But it's annoying in the long run.
Click to expand...
I haven't experienced this issue before. I'm also using MPC-HC.
I will try to run a test encoding later.

cartman0208 said:
Well ... usually black bars use VERY little space, because the information can be described as two rectangles with one colour, which can be saved with only some bytes.
Of course it's a bit more difficult, but the size should be less than 1% of the picture size.
20% difference is a bit strange though.
Click to expand...
I understand your point about the compression of uniform areas like black bars. They can be highly efficient and require minimal data to represent them due to their uniformity. The compression algorithms, especially in advanced codecs like HEVC, are pretty effective at minimizing the space these uniform sections occupy.

However, there are other factors to consider beyond just the space taken by the black bars themselves. Cropping black bars before encoding can change the overall dynamics of video compression. When these bars are removed, the encoder can allocate more of its available bitrate to the actual content, potentially enhancing the quality of the visible parts of the video. Alternatively, it can maintain the same quality with a lower bitrate, thus reducing the file size.

The impact on file size can vary significantly depending on the content's complexity, motion, and the chosen bitrate for encoding. In static or less complex scenes, the difference might indeed be minimal. But in more dynamic or detailed content, the efficiency gains from reallocating bitrate to actual content instead of black bars can be more pronounced.

So, while the direct impact of black bars on file size might be small due to efficient compression, the indirect effects on the encoding process and bitrate distribution can lead to noticeable differences in specific scenarios. A 10-25% figure might be on the higher side and more typical for cases where black bars take up a substantial portion of the frame and the content benefits significantly from bitrate reallocation post-cropping.


A quick test run with Indiana Jones and cropping black bars reduces file size by ca 12.30%.
1708549854452.png
 
James said:
Sounds to me like a player problem. What are you using for playback?
And if your player struggles with "strange" aspect ratios, just keep the black bars. They usually don't hurt, unless you have a fancy setup like a constant image height projector & screen setup.
Click to expand...
I have encountered an issue with the aspect ratio when removing black bars.
In a test example of Indiana Jones using CloneBD, the display aspect ratio created is 2.667 with an original display aspect ratio of 16:9.
The aspect ratio 1920x808 should be 2.3762, close to 2.40 or 21:9.
I removed the black bars manually, and the aspect ratio is around 2.40 for confirmation.
This discrepancy could lead to the Spatial Compression effect.
Please note that the log file for CloneBD is attached.
 

Attachments

  • CloneBD.1.3.2.1.Indiana Jones and the Kingdom of the Crystal Skull_crop_black_bars.cbdlog
    279.6 KB · Views: 2
IMO there should be no difference at all ... you set a target bitrate at the start of encoding...
so the resulting video should match that bitrate, cropped or not.
If it does not, there is something wrong with the bitrate calculation, I guess.
 
Hello everyone,
I am now sure that the problem with the spatial compression is a problem with the MPCHC media player. Which was not the case before. This was not the case before with the movies that I compressed afterwards with "Handbrake" and cropped the black bars. But now it is the case here too.
I have to select "Scaling for 16:9 display" for 16:9 films under "Pan & Scan" and then it works here. However, I always have to repeat this. The setting is not saved. With 21:9 it now also fits. Let's see. Maybe I'll reinstall the player later.

@tectpro: Thanks for the detailed explanation
 
gdc333 said:
You reprocessed the file when you removed the black bars. So you are comparing apples to applesauce.
Click to expand...
Uhm, what makes you think that?
The uncropped file is also reprocessed.
Unprocessed 1080p BDs are in AVC, the resulting files are both HEVC
 
cartman0208 said:
Uhm, what makes you think that?
The uncropped file is also reprocessed.
Unprocessed 1080p BDs are in AVC, the resulting files are both HEVC
Click to expand...
Right, I misread the screen cap. I thought the 820p file was recompressed.
 
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