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• sws_scale YUV —> RGB distorted image [closed]

  18 décembre 2024, par Sami susu

  I want to convert YUV420P image (received from H.264 stream) to RGB, while also resizing it, using sws_scale.
  
The size of the original image is 480 × 800. Just converting with same dimensions works fine.
  
But when I try to change the dimensions, I get a distorted image, with the following pattern :

  



  

  • changing to 481 × 800 will yield a distorted B&W image which looks like it's cut in the middle

  


  • 482 × 800 will be even more distorted

  


  • 483 × 800 is distorted but in color

  


  • 484 × 800 is ok (scaled correctly).

  


  



  Now this pattern follows - scaling will only work fine if the difference between divides by 4.

  



  Here's a sample code of the way that I decode and convert the image. All methods show "success".

  



  int srcX = 480;
int srcY = 800;
int dstX = 481; // or 482, 483 etc
int dstY = 800;

AVFrame* avFrameYUV = avcodec_alloc_frame();
avpicture_fill((AVPicture *)avFrameYUV, decoded_yuv_frame, PIX_FMT_YUV420P, srcX , srcY);

AVFrame *avFrameRGB = avcodec_alloc_frame();

AVPacket avPacket;
av_init_packet(&avPacket);
avPacket.size = read; // size of raw data
avPacket.data = raw_data; // raw data before decoding to YUV

int frame_decoded = 0;
int decoded_length = avcodec_decode_video2(g_avCodecContext, avFrameYUV, &frame_decoded, &avPacket);
int size = dstX * dstY * 3;

struct SwsContext *img_convert_ctx = sws_getContext(srcX, srcY, SOURCE_FORMAT, dstX, dstY, PIX_FMT_BGR24, SWS_BICUBIC, NULL, NULL, NULL);

avpicture_fill((AVPicture *)avFrameRGB, rgb_frame, PIX_FMT_RGB24, dstX, dstY);
sws_scale(img_convert_ctx, avFrameYUV->data, avFrameYUV->linesize, 0, srcY, avFrameRGB->data, avFrameRGB->linesize);

// draws the resulting frame with windows BitBlt
DrawBitmap(hdc, dstX, dstY, rgb_frame, size);

sws_freeContext(img_convert_ctx); 


  


• Extend plain background in a video

  3 juillet 2022, par Maiki

  Is there any easier way to achieve this ?, I'd like to make a .bat file that modify 148 videos that are 3840x2160

  


  They belong to the COLORFUL platform video set 1.8.0

  


  Every video has a system or console in the middle of it and it has a plain color as background. I want to keep the resolution, 3840x2160 but I need to displace the image a 15% to the right so it will be neccesary to fill the left area with the same color it's being use as color of the background.

  


  This is a snapshot from one of these videos :

  


  Snapshot of the original video

  


  The result should be something like this :

  


  Snapshot of the video I'd like to get

  


  So far I was trying lot of things with no success, I maybe did it harder than it is really. I did a first script that crop the video :

  


  for %%X in (*.mp4) do .\ffmpeg\bin\ffmpeg.exe -threads 4 -i "%%X" -filter:v "crop=2688:ih" -c:a copy -threads 4 "second_script\%%X"


  


  The new video will be stored in the second_script folder, then there is a second script that will use ffmpeg to export a picture from the video and magick.exe will help me to identify the color, after that it will use ffmpeg again to add an are of that color, but ... for some reason I don't know the color result is not the same

  


  for %%X in (*.mp4) do (
..\ffmpeg\bin\ffmpeg.exe -threads 4 -i "%%X" -vf "select=eq(n\,100)" -vframes 1 %%~nX.png

magick.exe .\%%~nX.png -format "%%[hex:u.p{0,0}]" info: > temp.txt

for /f "delims=" %%i in (temp.txt) do (
..\ffmpeg\bin\ffmpeg.exe -threads 4 -i "%%X" -filter_complex "[0]pad = w=3840 : h=ih: x=3840-2688 : y=0 : color=#%%i" -movflags +faststart  -c:a copy -threads 4 "final\%%X"
)

)


  


  What I get is something like this :

  


  Final result, it doesn't look like I expected

  


  Would there be any easy way to do this ? any recommendation is really appreciate

  


• invalid dropping st:0 and Non-monotonous DTS in output stream 0:1 errors in ffmpeg

  21 février 2020, par AlexZheda

  I would really be thankful if I could get help with the following.

  ffmpeg -f concat -safe 0 -i mylist.txt   
  
         -filter_complex "[0:v]setpts=.5*PTS[v1];
  
         [0:a]atempo=2,asetpts=N/SR/TB[a1]"
  
         -c:v h264_nvenc -map "[v1]" -map "[a1]"  x2_merged_vid.mp4

  But I get 2 errors and the resulting video is broken with the sound disappearing around the middle of the video.
  One type of the errors (there are loads of those) is this :

  [mp4 @ 0000019d21d66040] Non-monotonous DTS in output stream 0:1; previous: 28555274, current: 11264; changing to 28555275. This may result in incorrect timestamps in the output file.

  The other type of errors is like so :

  DTS 41437099, next:291253341916 st:0 invalid dropping
  
  PTS 41437099, next:291253341916 invalid dropping st:0

  The full log file is here.
  I am stumbled since I enforced asetpts=N/SR/TB, but the DTS and PTS are still not working properly..
  What else can I do to make it output a correct file ? I am not constrained in resources and can re-encode the whole thing frame by frame, but I cannot find how to do it.

  EDIT : It still does not work even with the approach of using concat filter. Same DTS/PTS errors.

      -filter_complex "[0:v:0][1:v:0]...[299:v:0]concat=n=300:v=1:a=0,fps=fps=30[cv1];
  
                           [0:a:0][1:a:0]...[299:a:0]concat=n=300:v=0:a=1,asetpts=N/SR/TB[ca1];
  
                     [cv1]setpts=0.25*PTS[v4];
  
                     [ca1]atempo=4,asetpts=N/SR/TB[a4]"
  
      -c:v h264_nvenc  -map "[v4]" -map "[a4]"  result.mp4 

  I have uploaded the logs outputs from the ffmpeg and ffprobe in [(filepath,json),(filepath,json),...] [here]2.
  I have been scratching my head why those PTS can’t be synced. Via ffprobe all v:0 and a:0 streams start from 0. I checked their stream0 and stream1 durations also and they also match. I also have a feeling that not all of the video files get concatenated in the resulting video. Maybe the issue is with the h264_nvenc ?