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• Node.js - Buffer Data to Ffmpeg

  24 septembre 2017, par user8568709

  I used Node.js and Ffmpeg to create animations. Because I was trying to avoid third-party avi/mp4 parsers, I decided to output the animation as raw rgb24 data file and then use some program to convert it to mp4 file.

  I found that Ffmpeg is free and open source which can do exactly it. So, I made a Node.js application which allocates a Buffer of size 1920 x 1080 x 3 (width times height times number of bytes per pixel), then I created a rendering context library, and finally I animated frame by frame and saved each frame consecutivelly in a binary file (using fs module).

  Then I invoked Ffmpeg to convert it to mp4 file and it works very good. Animations are pretty easy to make and Ffmpeg does its job correctly.

  However, the only problem is because it is very slow and eats space on hard disk. I want to create very long animations (more than a hour). The final mp4 file is relativelly small, but raw video file is extremelly big. About ninety percents of each frame are black pixels, so Ffmpeg comress it very good, but raw file cannot be compressed and it takes sometimes mor ethan 100 Gigabytes. Also, there is very unnecessary double processing same data. Firstly I process it in Node.js to save data to file, and then Ffmpeg reads it to convert it to mp4. There is a lot of unnecessary work.

  So, I’m looking for a way (and I’m pretty sure it is possible, but I didn’t find a way to do it yet) to output raw video data (one frame at a time) to Ffmpeg process (without saving anything to the hard disk).

  My goal is to do the following :

  1. Open Ffmpeg process
  2. Render a frame in Node.js
  3. Output raw byte stream to Ffmpeg
  4. Wait for Ffmpeg to encode it and append to mp4 file
  5. Let Ffmpeg wait for my Node.js process to render next frame

  ---

  Is there a way to achieve it ? I really don’t see a reason to post code, because my current code has nothing to do with the question I’m asking here. I don’t struggle with syntax errors or implementation problems. No, instead I just don’t know which parameters to pass to Ffmpeg process in order to achieve what I’ve already explained.

  I’ve searched in documentation to find out which parameters I need to pass to Ffmpeg process in order to let it read raw data from stdin instead from file, and also to wait until my Node.js process render next frame (so to disable time limit) because rendering a frame may take more than 24 hours. Therefore, Ffmpeg process should wait without time limit. However, I didn’t find anything about it in documentation.

  I know how to write to stdin from Node.js and similar technical stuff, so no need to explain it. The only question(s) here :

  1. Which parameters to pass to Ffmpeg ?
  2. Do I need to create Ffmpeg process (using child_process) with some special options ?

  ---

  Thank you in advance. Please, take it easy, this is my first question ! :)

• Artifacts after HEVC 10-bit encoding using NVENC

  18 juillet 2017, par Cryman

  Recently I purchased a brand new GPU - AORUS GeForce GTX 1080 Ti. I found out that it supports HEVC 10-bit encoding, so I wanted to give that a try. Unfortunately, after encoding I noticed some artifacts, which occur in dark scenes and last one frame of the video. You can see them on these screenshots :

  

  

  I was wondering if someone could help me figure out what might be the cause of these artifacts and how I can get rid of them.

  Here is the MI of the source video :

  ID                                       : 1
  
  Format                                   : AVC
  
  Format/Info                              : Advanced Video Codec
  
  Format profile                           : High@L4.1
  
  Format settings, CABAC                   : Yes
  
  Format settings, ReFrames                : 4 frames
  
  Codec ID                                 : V_MPEG4/ISO/AVC
  
  Duration                                 : 2 h 2 min
  
  Bit rate mode                            : Variable
  
  Bit rate                                 : 29.5 Mb/s
  
  Maximum bit rate                         : 37.0 Mb/s
  
  Width                                    : 1 920 pixels
  
  Height                                   : 1 080 pixels
  
  Display aspect ratio                     : 16:9
  
  Frame rate mode                          : Constant
  
  Frame rate                               : 23.976 (24000/1001) FPS
  
  Color space                              : YUV
  
  Chroma subsampling                       : 4:2:0
  
  Bit depth                                : 8 bits
  
  Scan type                                : Progressive
  
  Bits/(Pixel*Frame)                       : 0.593
  
  Stream size                              : 25.2 GiB (66%)
  
  Language                                 : English
  
  Default                                  : Yes
  
  Forced                                   : No

  And here is the MI of the encoded video :

  ID                                       : 1
  
  Format                                   : HEVC
  
  Format/Info                              : High Efficiency Video Coding
  
  Format profile                           : Main 10@L4@Main
  
  Codec ID                                 : V_MPEGH/ISO/HEVC
  
  Duration                                 : 2 h 2 min
  
  Bit rate                                 : 3 689 kb/s
  
  Width                                    : 1 920 pixels
  
  Height                                   : 800 pixels
  
  Display aspect ratio                     : 2.40:1
  
  Frame rate mode                          : Constant
  
  Frame rate                               : 23.976 (24000/1001) FPS
  
  Standard                                 : Component
  
  Color space                              : YUV
  
  Chroma subsampling                       : 4:2:0
  
  Bit depth                                : 10 bits
  
  Bits/(Pixel*Frame)                       : 0.100
  
  Stream size                              : 3.15 GiB (95%)
  
  Default                                  : Yes
  
  Forced                                   : No
  
  Color range                              : Limited

  The command I’m using for encoding :

  ffmpeg -hide_banner -i "" -map 0:v:0 -map_chapters -1 -map_metadata -1 -vf "crop=1920:800:0:140" -vcodec hevc_nvenc -pix_fmt p010le -preset hq -profile:v main10 -rc constqp -global_quality 21 -rc-lookahead 32 -g 240 -f matroska Video_CQP21_LAF32_GOP240.mkv

• How to compress output file using FFmpeg - Apple ProRes 422

  17 octobre 2018, par user1526912

  I am new to video encoding and trying to encode a music video for the apple itunes video store.

  I am currently using FFmpeg for encoding.

  My source file is mp4 file type and file size=650MB

  I encode the file using the Apple ProRes 422 (HQ) codec and output a mov file.

  ffmpeg -y -i busy1.mp4  -vcodec prores -profile:v 3 -r "29.97" -c:a mp2   busy2.mov

  I am trying to encode the video according to the following specs :

  ● Apple ProRes 422 (HQ)
  ● VBR expected at 220 Mbps

  Encoded PASP Converted to ProRes From
  1920 x 1080 1:1 HDCAM SR, D5, ATSC
  1280 x 720 1:1 ATSC progressive

  29.97 interlaced frames per second for video sourced

  Music Video Audio Source Profile

  ● MPEG-2 layer II stereo
  ● 384 kpbs
  ● 48Khz

  The file is encoded perfectly fine however the output is 6Gb in size.

  Why would the file be so large after encoding ?

  Am I doing something wrong here ?