How to compile from source code?

[artenax]

I have a lot of issues to go through, so in order to make it easier for me to help you, I ask that you please try these things first

• Check out all the menus and keyboard shortcuts. Maybe the feature already exists?
• Try with the newest version from GitHub
• Read the documentation and FAQ, Known issues, Troubleshooting to see if the feature already exists
• See if someone already suggested this under Issues or Discussions

Description

Provide instructions, please. I have Ubuntu 22.04. I would like to recompile the program and increase the bitrate, it is too low, poor quality.

Graph using plotbitrate:

[mifi]

Are you talking about smart cut bit rate?

https://github.com/mifi/lossless-cut/blob/master/.github/workflows/build.yml

[artenax]

build.yml

What should I do with this file? Will GitHub build it?

Are you talking about smart cut bit rate?

Yes.

[mifi]

What should I do with this file? Will GitHub build it?

yes you can either use github actions in your fork, or you can translate/run commands from that file locally on your computer

Are you talking about smart cut bit rate?

Yes.

I already increased bitrate by 20%, but maybe that was not enough: c01f0cf

see also existing discussions here: #126 (comment)

What does bit_rate and max_bit_rate metadata say on the file you're trying to smart cut?

[artenax]

I installed nodejs 18.18.2 in /usr/local
sudo npm install -g yarn

git clone https://github.com/mifi/lossless-cut
cd lossless-cut
git checkout abacff91a40e83002a7560cab481e372386141b3

In lossless-cut/src/smartcut.js
changed:
videoBitrate = Math.floor(videoBitrate * 1.2)
to:
videoBitrate = Math.floor(videoBitrate * 20)

yarn install
yarn build
yarn download-ffmpeg-linux-x64
yarn run
yarn start

The program starts slowly in this mode, I encountered a packaging problem.
Now everything is fine, bitrate is normal.

I had two video files:

1. WebM VP9 from YouTube.
2. MKV H.264 encoded by me with crf 18.

On both of them only multiplier 20 is good.
See how to build on the github server here.

[artenax]

I don't know how to use GitHub Actions, never tried it.
For packaging I have to create resources/app.asar it seems using the asar utility. I don't know exactly how.

[mifi]

Can you share info about your file? Multiplier 20 seems quite extreme. I wonder why such a multiplier is necesaary

[mifi]

Do your files by any chance have bit rate «N/A» for the video track?

[mifi]

I think there’s a bug in the code that estimates bitrate when bit_rate is N/A. It estimates bit rate from size/duration, but that is bytes/sec, ffmpeg -b expects bits, so we need to multiply by 8 here:

lossless-cut/src/smartcut.js

Line 46 in c01f0cf

videoBitrate = stats.size / videoDuration;

this also explains your high multiplier and also some people who complained about low quality some times

[mifi]

you can try new nightly build tomorrow if you like

[artenax]

Can you share info about your file?

The file is regular, downloaded from YouTube https://www.youtube.com/watch?v=RtFocW6gi5c with yt-dlp, streams 247+251, mux in ffmpeg 6.0. WebM (VP9 720p + Opus). I don't have much traffic left, please download it yourself.

General
Format                                   : WebM
Format version                           : Version 4
File size                                : 182 MiB
Duration                                 : 28 min 40 s
Overall bit rate                         : 889 kb/s
Writing application                      : Lavf60.3.100
Writing library                          : Lavf60.3.100

Video
ID                                       : 1
Format                                   : VP9
Codec ID                                 : V_VP9
Duration                                 : 28 min 40 s
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Color space                              : YUV
Language                                 : English
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

Audio
ID                                       : 2
Format                                   : Opus
Codec ID                                 : A_OPUS
Duration                                 : 28 min 40 s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Bit depth                                : 32 bits
Compression mode                         : Lossy
Language                                 : English
Default                                  : Yes
Forced                                   : No

Do your files by any chance have bit rate «N/A» for the video track?

How can I check this?
The MediaInfo utility does not really show either the video bitrate or the audio bitrate. Only the total. Since everywhere is VBR, and info tags ffmpeg does not insert (in webm/mkv). However, even repackaging in MKVToolnix didn't help. MKVToolnix inserted info tags (track statistic tags) and MediaInfo utility showed bitrate (video, audio, total), but only MediaInfo.

I think there’s a bug in the code that estimates bitrate when bit_rate is N/A. It estimates bit rate from size/duration, but that is bytes/sec, ffmpeg -b expects bits, so we need to multiply by 8 here

LosslessCut selects a bitrate 3 times lower. I checked.
More precisely, such bitrate is obtained in files after LosslessCut (in the transcoded area). I haven't looked at the exact command line. Since encoders may not always respect the specified bitrate.

you can try new nightly build tomorrow if you like

I could try. But I also like to choose the bitrate myself in my build.

[artenax]

I tried the nightly build. It's much better now. The bitrate is higher by a factor of x1.07 ... x1.37. This was clearly a bit/byte problem, which you fixed. Thanks.

I'd like the bitrate even higher, of course. Because I'm still seeing some artifacts.
YouTube uses VP9 more efficiently, probably with a hardware encoder.

[artenax]

The nightly builds have an expiration date and require a github account, so I've re-uploaded them. They may be useful for those who don't have a github account.

[mifi]

cool. note that nightly builds will eventually turn into an actual release