Video Compression Artifacts

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swbca3691
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Video Compression Artifacts

Post by swbca3691 » Sat Mar 25, 2017 6:08 pm

Testing a new phone GS7 and the current version of Laptimer, I just created a video driving around my neighborhood and then added the overlay.

The 1920 x 1080 overlay video has severe compression artifacts and the overlay file is less than half the size of the original video file.
The overlay video file from today is less than half the size of a 1920 x 1080 overlay video of the same length (3 minutes, 10 seconds) from last august.

I have never had compression artifacts in the past until testing this new phone and the current version of LapTimer.
I have run 3 tests today, and they all have the same problem.

Any Ideas?

Thanks
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Re: Video Compression Artifacts

Post by Harry » Sat Mar 25, 2017 8:14 pm

You can increase the bitrate by an arbitrary factor using Administration ‣ Settings ‣ Expert Settings ‣ Video Bitrate Multiplier. In case this does not help enough, you can switch back to software based video encoding (probably as used by your old phone before): Administration ‣ Settings ‣ Expert Settings ‣ Force Software Encoding.

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Re: Video Compression Artifacts

Post by swbca3691 » Sat Mar 25, 2017 9:44 pm

Is the initial video bitrate controlled by the LapTimer or just the Overlay ? The initial raw videos also have smaller file sizes than videos of the same frame size and time duration from last year. Then the file size of the overlay-videos get much smaller.

I will work on your suggestions. Thanks
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Re: Video Compression Artifacts

Post by Harry » Sat Mar 25, 2017 9:50 pm

The raw video's bitrate is not controlled by LapTimer. It just selects a FullHD preset in your case. The bitrate multiplier is used during overlaying (i.e. when the resulting overlaid video is encoded from changed frames).

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Re: Video Compression Artifacts

Post by swbca3691 » Sun Mar 26, 2017 3:40 am

SOLVED: The bitrate multiplier setting of "2" doubled the size of the file; a setting of "3" tripled the size of the file, but I could not see any improvement in the quality of the video. So, I switched to Software processing and it was excellent, as it was last year before hardware processing was available for Android. The file size is large however. A 3 minute overlayed video at 1920x1080 resolution is 820 MB. That's more the double the file size of the RAW 3 minute video.

Thanks for you help.
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Re: Video Compression Artifacts

Post by Harry » Sun Mar 26, 2017 8:02 am

Software encoding does not use the H.264 encoding like the hardware method, but the old MPG-4 Part 2. That's not the reason for the better quality, but the reason for the huge resulting size. You can convert it to H.264 using some converter, but this will certainly lose some quality due to the decoding / encoding again. I assume the loss in quality for the hardware approach is a limited color space of an intermediate format used during overlay.

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Re: Video Compression Artifacts

Post by swbca3691 » Mon Mar 27, 2017 7:01 pm

Forced Software processing causes a new problem that wasn't there last year . . huge file size

I switched to Software Processing because the hardware processing made a terrible video. Mostly seen when shading on the road surface changed. Lighting change would occur in big square blocks of grey and lighter grey moving around within the video image. I also notice that color rings would appear on smooth surfaces . . . like very low color depth.

I have a large library of 1280x720 track videos from last year. The file size of the Overlay Video is consistently 215MB (+/- 10MB) per minute of video.

Today I drove in an environment that would simulate being on the track and the resulting 1280x720 file sizes were 410MB per minute of video.
I did the test with my Galaxy S5 from last year and my new GS7. The results were the same.

Also in my tests, the RAW file size is 900,167 for a 10 minute video
The Overlay video files size is 4,066,508 for the same video

Another strange think. If I run the same test with 1920x1080 resolution the Overlay video was 460MB per minute of video . . not much larger than the 1280x720 overlay file size.

So why are the 1280x70 overlay video file sizes so large ? Is this from Android software updates since last year, or a change in Laptimer ?
Last edited by swbca3691 on Mon Mar 27, 2017 7:55 pm, edited 2 times in total.
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Re: Video Compression Artifacts

Post by Harry » Mon Mar 27, 2017 7:42 pm

Software encoding does not use the H.264 encoding like the hardware method, but the old MPG-4 Part 2.
MPG-4 Part 2 requires considerable more space for the same quality.

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