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• FFMPEG Api conversion from YUV420P to RGB produces strange output

  20 novembre 2024, par fasc8

  I'm using the FFMPEG Api in Rust to get RGB images from video files.

  


  While some videos work correct and I get the frames back as expected, some work not. Or at least the result is not the way I expected it to be.

  


  The code I use in Rust :

  


  ffmpeg::init().unwrap();

let in_ctx = input(&Path::new(source)).unwrap();
let input = in_ctx
    .streams()
    .best(Type::Video)
    .ok_or(ffmpeg::Error::StreamNotFound)?;

let decoder = input.codec().decoder().video()?;

let scaler = Context::get(
    decoder.format(),
    decoder.width(),
    decoder.height(),
    Pixel::RGB24,
    decoder.width(),
    decoder.height(),
    Flags::FULL_CHR_H_INT | Flags::ACCURATE_RND,
)?; // <--- Is basically sws_getContext

// later to get the actual frame
let mut decoded = Video::empty();
if self.decoder.receive_frame(&mut decoded).is_ok() {
    let mut rgb_frame = Video::empty();
    self.scaler.run(&decoded, &mut rgb_frame)?; // <--- Does sws_scale
    println!("Converted Pixel Format: {}", rgb_frame.format() as i32);
    Ok(Some(rgb_frame))
}


  


  Which should roughly translate to C like so :

  


  // Get the context and video stream
SwsContext * ctx = sws_getContext(imgWidth, imgHeight,
                              imgFormat, imgWidth, imgHeight,
                              AV_PIX_FMT_RGB24, 0, 0, 0, 0);
sws_scale(ctx, decoded.data, decoded.linesize, 0, decoded.height, rgb_frame.data, rbg_frame.linesize);


  


  And like I said earlier, sometimes it works fine and I get the expected frame back. But sometimes I get something like this :
Weird result image

  


  I saved the images as .ppm files for quick visual comparison. I used this method, which basically writes the bytes to a file with a simple .ppm header :

  


  fn save_file(frame: &Video, index: usize) -> std::result::Result<(), std::io::Error> 
{
    let mut file = File::create(format!("frame{}.ppm", index))?;
    file.write_all(format!("P6\n{} {}\n255\n", frame.width(), frame.height()).as_bytes())?;
    file.write_all(frame.data(0))?;
    Ok(())
}


  


  Here you can see that on the left side there is a good image result vs. on the right side there is a bad image result.
Comparison of the .ppm files

  


  To come to the question now :

  


  Why is this happening. I tested everything on my side and the only thing left is ffmpeg conversion. FFMPEG seems to convert these two test files differently even though it reports YUV420P as format for both. I cannot figure out what the difference may be...

  


  Here the info for the two video files i used :

  


  Good video file :

  


  General
Complete name                            : /mnt/smb/Snapchat-174933781.mp4
Format                                   : MPEG-4
Format profile                           : Base Media / Version 2
Codec ID                                 : mp42 (isom/mp42)
File size                                : 1.90 MiB
Duration                                 : 9 s 612 ms
Overall bit rate                         : 1 661 kb/s
Encoded date                             : UTC 2021-07-28 22:09:36
Tagged date                              : UTC 2021-07-28 22:09:36
eng                                      : -180.00

Video
ID                                       : 512
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L3.1
Format settings                          : CABAC / 1 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 1 frame
Format settings, GOP                     : M=1, N=30
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 9 s 598 ms
Bit rate                                 : 1 597 kb/s
Width                                    : 480 pixels
Height                                   : 944 pixels
Display aspect ratio                     : 0.508
Frame rate mode                          : Variable
Frame rate                               : 29.797 FPS
Minimum frame rate                       : 15.000 FPS
Maximum frame rate                       : 30.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.118
Stream size                              : 1.83 MiB (96%)
Title                                    : Snap Video
Language                                 : English
Encoded date                             : UTC 2021-07-28 22:09:36
Tagged date                              : UTC 2021-07-28 22:09:36
Color range                              : Full
colour_range_Original                    : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.601
transfer_characteristics_Original        : BT.709
Matrix coefficients                      : BT.709
Codec configuration box                  : avcC

Audio
ID                                       : 256
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : mp4a-40-2
Duration                                 : 9 s 612 ms
Bit rate mode                            : Constant
Bit rate                                 : 62.0 kb/s
Channel(s)                               : 1 channel
Channel layout                           : C
Sampling rate                            : 44.1 kHz
Frame rate                               : 43.066 FPS (1024 SPF)
Compression mode                         : Lossy
Stream size                              : 73.3 KiB (4%)
Title                                    : Snap Audio
Language                                 : English
Encoded date                             : UTC 2021-07-28 22:09:36
Tagged date                              : UTC 2021-07-28 22:09:36


  


  Bad video file :

  


  General
Complete name                            : /mnt/smb/Snapchat-1989594918.mp4
Format                                   : MPEG-4
Format profile                           : Base Media / Version 2
Codec ID                                 : mp42 (isom/mp42)
File size                                : 2.97 MiB
Duration                                 : 6 s 313 ms
Overall bit rate                         : 3 948 kb/s
Encoded date                             : UTC 2019-07-11 06:43:04
Tagged date                              : UTC 2019-07-11 06:43:04
com.android.version                      : 9

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : Baseline@L3.1
Format settings                          : 1 Ref Frames
Format settings, CABAC                   : No
Format settings, Reference frames        : 1 frame
Format settings, GOP                     : M=1, N=30
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 6 s 313 ms
Bit rate                                 : 3 945 kb/s
Width                                    : 496 pixels
Height                                   : 960 pixels
Display aspect ratio                     : 0.517
Frame rate mode                          : Variable
Frame rate                               : 29.306 FPS
Minimum frame rate                       : 19.767 FPS
Maximum frame rate                       : 39.508 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.283
Stream size                              : 2.97 MiB (100%)
Title                                    : VideoHandle
Language                                 : English
Encoded date                             : UTC 2019-07-11 06:43:04
Tagged date                              : UTC 2019-07-11 06:43:04
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709
Codec configuration box                  : avcC


  


  Or as a diff image :

  


  The problem is that I am not that familiar with ffmpeg yet I don't know all the quirks it has.

  


  I hope someone can point me in the right direction.

  


• How to schedule ffmpeg audio streams of varying lengths with titles and metadata ?

  10 septembre 2021, par underdoot

  I have a Shoutcast stream that I want to archive 24/7 with ffmpeg. Shows on this stream vary in length between 1-3 hours, but have a regular weekly schedule.

  


  How do I download these shows, and give the files appropriate titles according to the show playing (determined by day of week and hour of day) ? I want the title of files to be along the lines of "2021.09.21 - 0300-0400 — Radio Show Name" and automatically add to a set folder. I also want to run the program only once, and have it running in the background constantly.

  


• To all Matomo plugin developers : Matomo 4 is coming, make your plugin compatible now

  6 août 2020, par Matomo Core Team — Development

  We’re planning to release the first beta of Matomo 4 in a few weeks. For making it easy for Matomo users to be able to upgrade to this beta, it would be great if as many plugins on the Marketplace as possible would be already updated and compatible with Matomo 4. Then many users would be able to upgrade to the first beta without any issues.

  Presumably, as you put your plugin on our Marketplace, you want people to use it. Making your plugin compatible with Matomo 4 helps ensure that people will be able to find and keep using your plugin. If your plugin is not compatible with Matomo 4, your plugin will be automatically deactivated. We’ll be happy to help you achieve compatibility should there be any issue.

  How do I upgrade my Matomo to Matomo 4 ?

  If you have installed your Matomo development environment through git you can simply checkout the Matomo 4 branch “4.x-dev” by executing these commands :

  • git checkout 4.x-dev 
  • composer install

  Alternatively, you can also download the latest version directly from GitHub as a zip file and run composer install afterwards. 

  How do I upgrade my plugin to Matomo 4 ?

  • We recommend you create a new branch for your plugin that supports Matomo 4. For example a branch named “4.x-dev“. This way you will be able to make changes to your plugin for Matomo 3 and Matomo 4 and release separate versions.
  • Check out our migration guide from Matomo 3 to Matomo 4 and the list of all breaking changes.
  • Release a new version of your plugin in GitHub as usual.

  While there were many breaking changes in Matomo 4, most of our Platform APIs remain unchanged, and almost all changes are for rarely used APIs. Often to make your plugin compatible it will just be a matter of adjusting the “plugin.json” file (as mentioned in the migration guide).

  You can find all developer documentation on our developer zone which has already been updated for Matomo 4.

  How do I know my plugin changes were released successfully ?

  If you have configured an email address within your “plugin.json” file, then you will receive a confirmation or an error email within a few minutes. Alternatively, you can also check out your plugin page on the Marketplace directly. If the plugin release was successful, you will see additional links below the download button showing which versions your plugin is compatible with.

  

  How can I downgrade to Matomo 3 or switch between Matomo 3 and Matomo 4 ?

  To downgrade from Matomo 4 to Matomo 3 :

  • check out the “3.x-dev” branch 
  • run a composer install as usual. 
  • run the SQL statements from this downgrade guide to restore the previous MySQL schema.

  When will the final Matomo 4 release be available ?

  We estimate the final stable Matomo 4.0.0 release will be released in approx. 3 months.

  What’s new in Matomo 4 ?

  We don’t have a summary of the changes available just yet but you can see all closed issues within this release here.

  Any questions or need help ? 

  If you have any questions, or experience any problems during the migration don’t hesitate to get in touch with us. We’ll be happy to help get your plugin compatible and the update published. If you find any undocumented breaking change or find any step during the migration process not clear, please let us know as well.

  Thank you for contributing a plugin to the Marketplace and making Matomo better. We really appreciate your work !