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• Why can't I duplicate an MJPEG stream from a webcam to a V4L2 Loopback Device on Linux ?

  17 août 2021, par Chris White

  I'm trying to duplicate a USB webcam device V4L2 stream (/dev/video0) to a V4L2 Loopback Device (/dev/video99) at the highest resolution and framerate possible with the hardware available on a Raspberry Pi 4 running the latest Raspbian (also the minimum CPU load). I'm using FFMPEG version 7:4.1.6-1 deb10u1+rpt2 and v4l2loopback version 0.12.5.1.

  


  The output from :
ffmpeg -f v4l2 -list_formats all -i /dev/video0 gives me the following :

  


  [video4linux2,v4l2 @ 0xc1e1c0] Compressed:       mjpeg :          Motion-JPEG : 1600x1200 3264x2448 2592x1944 2048x1536 1280x960 1024x768 800x600 640x480 320x240 1600x1200
[video4linux2,v4l2 @ 0xc1e1c0] Raw       :     yuyv422 :           YUYV 4:2:2 : 1600x1200 3264x2448 2592x1944 2048x1536 1280x960 1024x768 800x600 640x480 320x240 1600x1200


  


  3264x2448px is the native CCD resolution, and the image is being used for machine vision purposes, so I'd like to use this maximum resolution at the highest framerate I can. The reason for the loopback device is so that I can view/stream the videofeed (with GStreamer) and take high resolution PNG snapshots simultaneously, using the command ffmpeg -f v4l2 -video_size 3264x2448 -i /dev/video99 -frames 1 capture.png -y From my understanding this means there is an MJPEG stream at this resolution and according to the command v4l2-ctl -d /dev/video0 --list-formats-ext I can manage 15fps :

  


  ioctl: VIDIOC_ENUM_FMT
    Type: Video Capture

    [0]: 'MJPG' (Motion-JPEG, compressed)
        Size: Discrete 1600x1200
            Interval: Discrete 0.067s (15.000 fps)
            Interval: Discrete 0.067s (15.000 fps)
        Size: Discrete 3264x2448
            Interval: Discrete 0.067s (15.000 fps)
        Size: Discrete 2592x1944
            Interval: Discrete 0.067s (15.000 fps)
        Size: Discrete 2048x1536
            Interval: Discrete 0.067s (15.000 fps)
        Size: Discrete 1280x960
            Interval: Discrete 0.067s (15.000 fps)
        Size: Discrete 1024x768
            Interval: Discrete 0.033s (30.000 fps)
        Size: Discrete 800x600
            Interval: Discrete 0.033s (30.000 fps)
        Size: Discrete 640x480
            Interval: Discrete 0.033s (30.000 fps)
        Size: Discrete 320x240
            Interval: Discrete 0.033s (30.000 fps)
        Size: Discrete 1600x1200
            Interval: Discrete 0.067s (15.000 fps)
            Interval: Discrete 0.067s (15.000 fps)
    [1]: 'YUYV' (YUYV 4:2:2)
        Size: Discrete 1600x1200
            Interval: Discrete 0.100s (10.000 fps)
            Interval: Discrete 0.100s (10.000 fps)
        Size: Discrete 3264x2448
            Interval: Discrete 0.500s (2.000 fps)
        Size: Discrete 2592x1944
            Interval: Discrete 0.333s (3.000 fps)
        Size: Discrete 2048x1536
            Interval: Discrete 0.333s (3.000 fps)
        Size: Discrete 1280x960
            Interval: Discrete 0.100s (10.000 fps)
        Size: Discrete 1024x768
            Interval: Discrete 0.100s (10.000 fps)
        Size: Discrete 800x600
            Interval: Discrete 0.033s (30.000 fps)
        Size: Discrete 640x480
            Interval: Discrete 0.033s (30.000 fps)
        Size: Discrete 320x240
            Interval: Discrete 0.033s (30.000 fps)
        Size: Discrete 1600x1200
            Interval: Discrete 0.100s (10.000 fps)
            Interval: Discrete 0.100s (10.000 fps)


  


  I feel like I've tried every possible version of GStreamer/FFMPEG command to achieve this and have had varying success, but more often than not I come up against "av_interleaved_write_frame() : Cannot allocate memory" or some issue with converting M-JPEG to rawvideo for the loopback device...

  


  What command should I be using ? I'm at the end of my tether !

  


  I've tried :

  


  gst-launch-1.0 v4l2src device=/dev/video0 ! "image/jpeg,width=3264,height=2448,framerate=15/1" ! avdec_mjpeg ! "video/x-raw,format=YUY2,width=3264,height=2448,framerate=15/1" ! v4l2sink device=/dev/video99


  


  and

  


  ffmpeg -f v4l2 -video_size 3264x2448 -i /dev/video0 -vcodec rawvideo -pix_fmt yuyv422 -r 1 -f v4l2 /dev/video99


  


  (EDIT) gives :

  


  ffmpeg version 4.1.6-1~deb10u1+rpt2 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 8 (Raspbian 8.3.0-6+rpi1)
  configuration: --prefix=/usr --extra-version='1~deb10u1+rpt2' --toolchain=hardened --incdir=/usr/include/arm-linux-gnueabihf --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-omx-rpi --enable-mmal --enable-neon --enable-rpi --enable-vout-drm --enable-v4l2-request --enable-libudev --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared --libdir=/usr/lib/arm-linux-gnueabihf --cpu=arm1176jzf-s --arch=arm
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 14226.770484, bitrate: 255688 kb/s
    Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 3264x2448, 255688 kb/s, 2 fps, 2 tbr, 1000k tbn, 1000k tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> rawvideo (native))
Press [q] to stop, [?] for help
Output #0, video4linux2,v4l2, to '/dev/video99':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 3264x2448, q=2-31, 127844 kb/s, 1 fps, 1 tbn, 1 tbc
    Metadata:
      encoder         : Lavc58.35.100 rawvideo
av_interleaved_write_frame(): Cannot allocate memory
frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:01.00 bitrate=N/A speed=15.8x    
video:15606kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Conversion failed!


  


  and

  


  ffmpeg -f v4l2 -video_size 3264x2448 -i /dev/video0 -vcodec rawvideo -pix_fmt yuv420p -r 15 -f v4l2 /dev/video99


  


  (EDIT) gives :

  


  ffmpeg version 4.1.6-1~deb10u1+rpt2 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 8 (Raspbian 8.3.0-6+rpi1)
  configuration: --prefix=/usr --extra-version='1~deb10u1+rpt2' --toolchain=hardened --incdir=/usr/include/arm-linux-gnueabihf --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-omx-rpi --enable-mmal --enable-neon --enable-rpi --enable-vout-drm --enable-v4l2-request --enable-libudev --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared --libdir=/usr/lib/arm-linux-gnueabihf --cpu=arm1176jzf-s --arch=arm
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 13704.103283, bitrate: 255688 kb/s
    Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 3264x2448, 255688 kb/s, 2 fps, 2 tbr, 1000k tbn, 1000k tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> rawvideo (native))
Press [q] to stop, [?] for help
Output #0, video4linux2,v4l2, to '/dev/video99':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 3264x2448, q=2-31, 1438248 kb/s, 15 fps, 15 tbn, 15 tbc
    Metadata:
      encoder         : Lavc58.35.100 rawvideo
av_interleaved_write_frame(): Cannot allocate memory
    Last message repeated 7 times
frame=    8 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.53 bitrate=N/A dup=7 drop=0 speed=1.37x    
video:93636kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Conversion failed!


  


  and

  


  ffmpeg -f v4l2 -input_format mjpeg -i /dev/video0 -vcodec copy -f v4l2 /dev/video99


  


  (EDIT) gives :

  


  ffmpeg version 4.1.6-1~deb10u1+rpt2 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 8 (Raspbian 8.3.0-6+rpi1)
  configuration: --prefix=/usr --extra-version='1~deb10u1+rpt2' --toolchain=hardened --incdir=/usr/include/arm-linux-gnueabihf --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-omx-rpi --enable-mmal --enable-neon --enable-rpi --enable-vout-drm --enable-v4l2-request --enable-libudev --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared --libdir=/usr/lib/arm-linux-gnueabihf --cpu=arm1176jzf-s --arch=arm
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
[mjpeg @ 0xdb5240] EOI missing, emulating
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 12511.425271, bitrate: N/A
    Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 3264x2448, 15 fps, 15 tbr, 1000k tbn, 1000k tbc
[video4linux2,v4l2 @ 0xdb7f10] V4L2 output device supports only a single raw video stream
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
    Last message repeated 1 times


  


  I'm not sure what to troubleshoot next - looking at available memory, there's no problem, so what am I doing wrong ? This copy of the feed is the last piece of the puzzle...

  


• ProcessBuilder is not called when trying to start a process

  15 juin 2022, par xnok

  I am trying to understand more about the ffmpeg usage in JavaCV for android studio and for said task I am trying to use ProcessBuilder. I tried writting a simple program to debug the pb.start(); Although, I am not getting a response. What I did was to start a default/empty activity and pasted the following program :

  


  package com.example.myapplication;

import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;

import org.bytedeco.javacpp.Loader;

import android.os.Build;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends AppCompatActivity {
    static final int cols = 192;
    static final int rows = 108;
    static final String ffmpeg = Loader.load(org.bytedeco.ffmpeg.ffmpeg.class);
    static final String rtmp_url = "test.flv";
    static final String[] command = {ffmpeg,
            "-y",
            "-f", "rawvideo",
            "-vcodec", "rawvideo",
            "-pix_fmt", "bgr24",
            "-s", (Integer.toString(cols) + "x" + Integer.toString(rows)),
            "-r", "10",
            "-i", "pipe:",
            "-c:v", "libx264",
            "-pix_fmt", "yuv420p",
            "-preset", "ultrafast",
            "-f", "flv",
            rtmp_url};
    @RequiresApi(api = Build.VERSION_CODES.O)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        new Thread(t1).start();

    }
    private static Runnable t1 = () -> {
        Log.e("TAG", "void OnCreate called successfully!");
        ProcessBuilder pb = new ProcessBuilder(command).redirectErrorStream(true);
        pb.redirectErrorStream(true);
        try {
            Process process = pb.start();
            BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
            OutputStream writer = process.getOutputStream();
            Log.e("TAG", "Something good happened here");
        } catch (IOException e) {
            e.printStackTrace();
            Log.e("TAG", "Nothing good happened here");
        }
    };


}


  


  My current problem is that I can't seem to start properly the processBuilder process via pb.start() ;

  


  I get the following logs from the logcat panel :

  


  2022-06-14 17:24:46.328 13371-13371/com.example.myapplication E/TAG: void OnCreate called successfully!
2022-06-14 17:24:46.333 13371-13371/com.example.myapplication E/TAG: Nothing good happened here


  


  I'd like to understand why is it skipping the try/catch block and not starting the process ?

  


  EDIT : I made some changes as per @g00se's suggestions and I got the following stack trace from the code above :

  


  2022-06-15 00:32:26.700 29787-29787/? E/USNET: USNET: appName: com.example.myapplication
2022-06-15 00:32:29.328 29787-29828/com.example.myapplication E/TAG: void OnCreate called successfully!
2022-06-15 00:32:29.330 29787-29828/com.example.myapplication E/AndroidRuntime: FATAL EXCEPTION: Thread-4
    Process: com.example.myapplication, PID: 29787
    java.lang.NullPointerException
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:1012)
        at com.example.myapplication.MainActivity.lambda$static$0(MainActivity.java:48)
        at com.example.myapplication.MainActivity$$ExternalSyntheticLambda0.run(Unknown Source:0)
        at java.lang.Thread.run(Thread.java:920)


  


• avformat/dhav : fix backward scanning for get_duration and optimize seeking

  21 mars, par Justin Ruggles

  avformat/dhav : fix backward scanning for get_duration and optimize seeking
  The backwards scanning done for incomplete final packets should not
  
  assume a specific alignment at the end of the file. Truncated files
  
  result in hundreds of thousands of seeks if the final packet does not
  
  fall on a specific byte boundary, which can be extremely slow.
  
  For example, with HTTP, each backwards seek results in a separate
  
  HTTP request.
  This changes the scanning to check for the end tag 1 byte at a time
  
  and buffers the last 1 MiB to avoid additional seek operations.
  Co-authored-by : Derek Buitenhuis <derek.buitenhuis@gmail.com>
  
  Signed-off-by : Justin Ruggles <justinr@vimeo.com>
  
  Signed-off-by : Derek Buitenhuis <derek.buitenhuis@gmail.com>
  

  • [DH] libavformat/dhav.c