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• Separate simultaneously changing regions of video into individual videos

  17 juillet 2019, par Elle Fie

  Given a single video stream (up to 4K resolution), where only small displayed portions may change, I’d like to identify these changing sections and create separate video streams, one for each changing section of the input video stream, in real time.

  Note that this is spatial extraction, not time slicing !

  Q1 : Is there a better name to address this process ?

  Q2 : Is this an already solved problem ?

  It seems ImageMagick’s Compare program supports diffing two images, which I can process to identify regions as coordinates for an ffmpeg crop (launched in parallel for each discovered diff region), but this method relies on having a PNG stream to avoid false positive diffs due to lossy encoding. Also, too slow to happen in real time.

  Q3 : Is there any way ffmpeg can dump out the causal regions influencing scene-change detection ?

• Capturing actual video stream quality using FFmpeg and FFplay – smooth recording but stuttering stream

  3 décembre 2024, par Karlitos Bemowo

  I’m trying to analyze the quality of a video stream over a local network using FFmpeg. My goal is to capture the actual streamed video (with all artifacts, stuttering, or buffering) as experienced in real-time, rather than a reconstructed, smooth output. Currently, the recorded video is perfectly smooth, but the live stream played using ffplay exhibits noticeable stuttering. Additionally, while the duration of the recording matches the original video, the live stream lasts longer, likely due to buffering caused by network instability.

  


  Here are the commands I’m using :
Sender :
ffmpeg -re -i file.mp4 -c:v libx265 -preset veryfast -f mpegts udp ://192.168.1.26:1234
Receiver :
ffmpeg -i udp ://192.168.1.10:1234 -c copy received_fhd.mp4 -fflags nobuffer

  


  The recorded file received_fhd.mp4 plays back perfectly, with no stuttering or frame drops, even though the network stream has visible issues when viewed in real-time with ffplay.The recorded file has the same duration as the original video (fhd.mp4), while the real-time stream playback with ffplay takes longer, suggesting delays caused by buffering or network issues. Same issue with with other codes for example vp9.

  


  GOAL : I want to capture the actual streamed video as experienced in real-time, with all stuttering, buffering, and artifacts included. This would allow me to analyze the network's impact on the video quality effectively.

  


  Questions :

  


  

  1. How can I modify my commands to record the video stream exactly as it is experienced in real-time, including any network-induced issues ?

  


  2. Is there a way to configure FFmpeg to behave more like ffplay in terms of handling and recording the stream ?

  


  


  Any guidance or alternative approaches would be greatly appreciated. Thank you !

  


  Experimented with different codecs (e.g., H.265, VP9) and output formats. Older codes has no delay in tranmission so I didn't notice the issue at frist.

  


  Explored various ffmpeg options like -fflags nobuffer and -c copy (as documentation says " For example, -codec copy or -codec : copy would copy all the streams without reencoding."), but it still doesn’t replicate the actual stream behavior.

  


• avcodec/utvideodec : use cached bitstream reader everywhere except on x86_32

  3 avril 2018, par Paul B Mahol

  avcodec/utvideodec : use cached bitstream reader everywhere except on x86_32
  From 100x real-time decoding to 138x real-time decoding for 320x240 video.
  Signed-off-by : Paul B Mahol <onemda@gmail.com>
  

  • [DH] libavcodec/utvideodec.c