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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 ! :)

• Raspberry Pi Camera Module - Stream to LAN

  20 août 2015, par user3096434

  have a little problem with the setup of my RasPi camera infrastructure. Basically I have a RPi 2 which shall act as a MontionEye server from now on and 2 Pi B+ with camera modules.

  Previously, when I had only one camera in my network, I used the following command to stream the output from RPi B+ camera module to Youtube in full HD. So far, this command works flawless :

  raspivid -n -vf -hf -t 0 -w 1920 -h 1080 -fps 30 -b 3750000 -g 50 -o - | b ffmpeg -ar 8000 -ac 2 -acodec pcm_s16le -f s16le -ac 2 -i /dev/zero -f h264 -i - -vcodec copy -acodec aac -ab 64k -g 50 -strict experimental -f flv $RTMP_URL/$STREAM_KEY 

  Now I have a 2nd RPi with a camera module and figured it might be the time for a change towards motioneye, as I then can view both/all camera’s in my network within the same software. I have motioneye installed on my RPi 2 and the software is running correctly.

  I have a little problem when it comes to access the data stream from the RPi B+ camera on my local network.

  Basically I cannot seem to figure out how to change the ffmpeg portion of the above mentioned command, in a way so it will stream the data to localhost (Or the RPi2 IP where motioneye runs - which one to use ?) instead of Youtube or any other videohoster.

  I wonder, if changing the following part is a correct assumption :

  Instead of using variables to define Youtube URL and key

  -f flv $RTMP_URL/$STREAM_KEY 

  And change this to

  -f flv 10.1.1.11:8080 

  Will I then be able to add this RPi B+ video stream to my RPi 2 motioneye server, by using motioneye ’add network camera’ function ?

  From my understanding I should be able to enter the following details into motioneye ’add network camera’wizard :

  Camera type: network camera
  
  RTSP-URL: 10.1.1.11:8080
  
  User: Pi
  
  Pass: [my pwd]
  
  Camera: [my ffmpeg stream shall show here]

  Thanks in advance !

  Uhm, and then... How do I forwarded the video stream from a given camera connected to motioneye ? Like from motioneye to youtube (or similar), without re-encoding the stream ?

  Like the command shown above streams directly to youtube. But I want to have it in a way, that video is streamed to local network/motioneye server, and from there I can decide which camera’s stream and when I want to send the videostream to youtube ?

  How would a RPi professional realize this ?

  The command above explained : Takes full HD video with 30 fps from Pi camera module and hardware encodes it on GPU with 3.75mbit/s. Then I streamcopy the video (no re-encoding) and add some audio, so that the stream complies with youtube rules (yes, no live stream without audio). Audio is taken from virtual SB16 /dev/zero at low sampling rate then encoded to 32k AAC and sent to youtube. Works fine xD.

  Just when I have like 3 or more of these RPi cams the youtube stream approach ain’t feasible anymore, as my DSL upstream is limited (10 mbit/s=. Thus I need motioneye server and some magic, so I can watch f.e. all 3 camera’s videostream and then motioneye server can select and streamcopy the video from the Pi’s cam I choose and send it to youtube, as the original command did.

  Any help, tips, links to similar projects highly appreciated.

  Again, many thanks in advance, and even more thanks just cause you read until here.

  —mx

• Ffmpeg - How to force MJPEG output of whole frames ?

  27 août 2021, par Maoration

  I'm working with ffmpeg to process an incoming MPEGTS stream from remote cameras, and deliver it to multiple clients using my app.

  



  Technically, I'm using ffmpeg to convert the incoming stream to an MJPEG output, and piping the data chunks (from the ffmpeg process stdout) to a writeable stream on the client http response.

  



  However, I'm facing a problem- not all data chunks represent a full 'whole' frame. thus, displaying them in a row in the browser, results in a flickering video, with half-complete frames, on a random basis.
I know this because when printing each chunk length, results most of the time in a big value (X), but every now and then I get 2 consecutive chunks with length (2/5X) followed by (3/5X) for example.

  



  So the question - is there a way to force the ffmpeg process to output only whole frames ? if not, is there a way for me to check each data chunk 'manually' and look for headers/metadata/flags to indicate frame start/end ?

  



  ---

  



  my ffmpeg command for outputting MJPEG is :

  



  ffmpeg -i - -c:v mjpeg -f mjpeg -


  



  explained :

  



  "-i -" : (input) is the stdin of the process (and not a static file)

  



  "-c:v mjpeg" : using the mjpeg codec

  



  "-f mjpeg" : output will be in the mjpeg format

  



  "-" : output not specified (file or url) - will be the process stdout

  



  ---

  



  Edit :
here are some console.log prints to visualize the problem :

  



  %%% FFMPEG Info %%%
frame=  832 fps= 39 q=24.8 q=29.0 size=   49399kB time=00:00:27.76 bitrate=14577.1kbits/s speed=1.29x    
data.length:  60376
data.length:  60411
data.length:  60465
data.length:  32768
data.length:  27688
data.length:  32768
data.length:  27689
data.length:  60495
data.length:  60510
data.length:  60457
data.length:  59811
data.length:  59953
data.length:  59889
data.length:  59856
data.length:  59936
data.length:  60049
data.length:  60091
data.length:  60012
%%% FFMPEG Info %%%
frame=  848 fps= 38 q=24.8 q=29.0 size=   50340kB time=00:00:28.29 bitrate=14574.4kbits/s speed=1.28x    
data.length:  60025
data.length:  60064
data.length:  60122
data.length:  60202
data.length:  60113
data.length:  60211
data.length:  60201
data.length:  60195
data.length:  60116
data.length:  60167
data.length:  60273
data.length:  60222
data.length:  60223
data.length:  60267
data.length:  60329
%%% FFMPEG Info %%%
frame=  863 fps= 38 q=24.8 q=29.0 size=   51221kB time=00:00:28.79 bitrate=14571.9kbits/s speed=1.27x  


  



  As you can see, a whole frame is about 60k (my indication is a clean video stream i'm viewing on the browser), but every now and then the output consists of 2 consecutive chunks that add up to 60k. when delivered to the browser, these are 'half frames'.