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• FFmpeg - Low/unstable encoding speed

  12 février 2023, par Erwan

  Trying to transcode two streams into one gives me poor/unstable encoding speeds from x0.400 to x0.988, sometimes above x1.

  


  fmpeg \
   -thread_queue_size 15 -rtbufsize 100M -i "https://.../stream.m3u8" \
   -thread_queue_size 15 -rtbufsize 100M -i "http://.../video.mjpg" \
   -filter_complex \
   "[0:v]setpts=PTS-STARTPTS [bg]; \
    [1:v]scale=200:-1,setpts=PTS-STARTPTS [fg]; \
    [bg][fg]overlay=W-w-10:10" \
   -c:v mpeg1video \
   -b:v 1000k \
    -r 25 \
   -threads 1 \
   -f mjpeg udp://127.0.0.1:1235?pkt_size=1316


  


  Hardware specs :

  


  

  • CPU is Intel Core 2 Duo

  


  • Mechanical hard drive

  


  


  I choose the mpeg1video encoder because of the low CPU usage. It seems that my Core 2 Duo can't keep up with libx264 .

  


  I played with output bitrates, fps and threads, -re but nothing seems to improve and stabilize encoding speed to x1. Which parameters do I need to change/add/remove to achieve a reliable x1 encoding speed ?

  


  Input streams are not reliable, download internet connection is slow and unreliable.

  


• In what way does this HEVC video not comply to Apples's requirements document ?

  16 novembre 2022, par Duke Dougal

  My goal is to work out why a given video file does not play on Macos/Safari/Quicktime.

  


  The background to this question is that it is possible to play HEVC videos with a transparent background/alpha channel on Safari/MacOS. To be playable, a video must meet the specific requirements set out by Apple in this document :

  


  https://developer.apple.com/av-foundation/HEVC-Video-with-Alpha-Interoperability-Profile.pdf

  


  The video that does not play on Apple/Safari/Quicktime is an HEVC video with an alpha transparency channel. Note that VLC for MacOS DOES play this file. Here it is :

  


  https://drive.google.com/file/d/1ZnXjcDbk-_YxTgRuH_D7RSR9SXdY_XTv/view?usp=share_link

  


  I have two example HEVC video files with a transparent background/alpha channel, and they both play fine using either Quicktime player or Safari :

  


  Working video #1 :

  


  https://drive.google.com/file/d/1PJAyg_sVKVvb-Py8PAu42c1qm8l2qCbh/view?usp=share_link

  


  Working video #2 :

  


  https://drive.google.com/file/d/1kk8ssUyT7qAaK15afp8VPR6mIWPFX8vQ/view?usp=sharing

  


  The first step is to work out in what way my non-working video ( https://drive.google.com/file/d/1ZnXjcDbk-_YxTgRuH_D7RSR9SXdY_XTv/view?usp=share_link ) does not comply with the specification.

  


  Once it is clear which requirements are not met by the non-working video then I can move onto the next phase, which is to try to formulate an ffmpeg command that will output a video meeting the requirements.

  


  I have read Apples requirements document and I am out of my depth in trying to analyse the non working video against the requirements - I don't know how to do it.

  


  Can anyone suggest a way to identify what is wrong with the video ?

  


  Additional context is that I am trying to find a way to create Apple/MacOS compatible alpha channel / transparent videos using ffmpeg with hevc_nvenc running on an Intel machine. I am aware that Apple hardware can create such videos, but for a wide variety of reasons it is not practical for me to use Apple hardware to do the job. I have spent many hours trying all sorts of ffmpeg and ffprobe commands to try to work out what is wrong and modify the video to fix it, but to be honest most of my attempts are guesswork.

  


• FFMPEG drops supposedly corrupt frames from original video while transcoding using h264 encoder

  19 février 2019, par t6nand

  I am using h264 for optimising MP4 for web. I have a video which has some supposedly corrupt frame(s) within it’s initial 1-2 seconds. (Frame provided below)

  On transcoding using :

  ffmpeg -i orig.mp4 -c:v libx264 -crf 25 -vf scale="-2:min(ih\,720)" -b:v 600K -g 90 -c:a libfdk_aac output.mp4

  The output MP4 has these frames dropped out and I have my output with it’s start about 1 to 2 seconds delayed from original video, thus resulting in overall less time duration in output video.

  Moreover, most media players also skip these frames in playback (like quicktime player, etc). But VLC media player was able to play this video without skipping these frames.

  Is there a way to not drop frames using ffmpeg ? And if possible is it possible to identify and fix these frames in a video ?

  Note : I tried encoding same video using AWS Elastic transcoder which actually fixed these frames (Frame provided below) :
  

  Note : Original video can be found here -
  https://drive.google.com/file/d/0B9VkhR9Zu60ybXFDeno3RGpQTUE/view?usp=sharing
  Video transcoded by AWS Elsatic transcoder can be found here -
  https://drive.google.com/file/d/0B9VkhR9Zu60yWUVHQk5MTk05QVk/view?usp=sharing

  EDIT1 : As suggested by @Mulvya in comments, TS-transcoded video can be found here - (https://drive.google.com/file/d/0B9VkhR9Zu60yU0t6T0dMME9ZMmc/view?usp=sharing)