bytedeco/javacv

FFmpegFrameGrabber's png image pipeline decodes dropped frames

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#2,025 opened on May 15, 2023

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Description

This is my image input pseudocode

int inputCount=0;
whlie(true) {
   byte[] imageBytes = producePngImage();
   if (inputBytes.length == 0) {
       continue;
   }
   pipeOutputStream.write(imageBytes);
   inputCount++;
}

this is my FFmpegFrameGrabber's pseudocode

FFmpegFrameGrabber g= new FFmpegFrameGrabber(pipeInputStream, 0);
g.setImageWidth(width);
g.setImageheight(height);
g.setImageMode(ImageMode.RAW);
g.setFormat("image2pipe");
g.setPixelFormat(AV_PIX_FMT_BGR24);
g.start()

Frame frame;
int count=0
while((frame = g.grab()) != null) {
   count++;
   recorder.record(frame);
}

But the above two counters inputCount are not equal to count, always 16 frames less

Contributor guide

Research direction
Investigate the frame dropping in FFmpegFrameGrabber's image2pipe pipeline. Check if the issue is due to buffer size, frame skipping in FFmpeg, or incorrect configuration of image format and pixel format. Compare input and output counters to identify where frames are lost. Consider using a synchronous pipe or adding a delay between writes.
Tech stack
java
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
JavaFFmpeg
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65