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• Sending frames from memory to FFMPEG command line program .NET 6

  15 septembre 2021, par Alessandro Martinelli

  I'm trying to use the pipe to send frames generated by my program to ffmpeg command line utility without saving them on disk. Please note I was able to generate a video by first saving frames on disk as images and then having FFMPEG generate a video from such images, but that approach is worse performance-wise and implies writing more data on SSD.

  


  I could use the help of this post, but I have FFMPEG returning an error on frame size, and I don't know how to solve it.

  


  My code is the following :

  


  //object storing single frame returned from camera
mv.impact.acquire.Request pRequest; 
string outputPath = ...;
List frames = new List();

[...]

// Single frame is saved into memory
MemoryStream stream = new MemoryStream();
using (RequestBitmapData data = pRequest.bitmapData) {
    data.bitmap.Save(stream, System.Drawing.Imaging.ImageFormat.Bmp);
    // Please note that now printing data.bitmap.PixelFormat would return Format24bppRgb
}
frames.Add(stream.ToArray());

[...] 

Console.WriteLine(frames.Count + " frames collected. First one length is " + frames.First().Length);

string ffmpegArgument = "/C " + _ffmpegPath + "\\ffmpeg -y -f rawvideo -pix_fmt rgb24 -framerate 3 -video_size 728x544 -i - -c:v libx264 -preset 9 -c:a libvo_aacenc " + outputPath;

Process cmd = new Process();
cmd.StartInfo.FileName = "cmd.exe";
cmd.StartInfo.Arguments = ffmpegArgument;
cmd.StartInfo.UseShellExecute = false;
cmd.StartInfo.RedirectStandardError = false;
cmd.StartInfo.RedirectStandardInput = true;

Console.WriteLine("Executing command " + ffmpegArgument + "...");
cmd.Start();
foreach (byte[] frame in frames) {
        cmd.StandardInput.Write(frame);
}
cmd.StandardInput.Flush();
cmd.StandardInput.Close();


  


  However, when I execute the program, I have the following output :

  


  492 frames collected. First one length is 1188150
Executing command /C ExternalTools\FFmpeg\ffmpeg -y -f rawvideo -pix_fmt rgb24 -framerate 32 -video_size 728x544 -i - -c:v libx264 -preset ultrafast -c:a libvo_aacenc -b:a 128k "Output\TemporaryVideo\2021-09-13 18_58_58.mp4"...
ffmpeg version 2021-06-27-git-49e3a8165c-essentials_build-www.gyan.dev Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 10.3.0 (Rev2, Built by MSYS2 project)

[...] (configurations)

[rawvideo @ 00000241d34feac0] Packet corrupt (stream = 0, dts = 0).
Input #0, rawvideo, from 'pipe:':
  Duration: N/A, start: 0.000000, bitrate: 304152 kb/s
  Stream #0:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 728x544, 304152 kb/s, 32 tbr, 32 tbn
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
pipe:: corrupt input packet in stream 0
[rawvideo @ 00000241d3511640] Invalid buffer size, packet size 6396 < expected frame_size 1188096
Error while decoding stream #0:0: Invalid argument

[...] (cpu capabilities)

Output #0, mp4, to 'Output\TemporaryVideo\2021-09-13 18_58_58.mp4':
  Metadata:
    encoder         : Lavf59.3.101
  Stream #0:0: Video: h264 (avc1 / 0x31637661), yuv444p, 728x544, q=2-31, 32 fps, 16384 tbn
    Metadata:
      encoder         : Lavc59.2.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
frame=    0 fps=0.0 q=0.0 Lsize=       0kB time=00:00:00.00 bitrate=N/A speed=   0x
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Conversion failed!


  


  The value expected by FFMPEG seems correct (1188096 = 728 x 544 x 3), but I don't understand where FFMPEG gets that "packet size 6396" from. Furthermore, that value (6396) changes at every program execution.

  


  I'm pretty sure frames are not corrupted since, if I save such frames on disk, the image is generated correctly.

  


  Thank you for your time,
Alessandro

  


• How to stream cv2.VideoWriter frames to and RTSP server

  10 juin 2022, par chasez0r

  Environment : Docker, Ubuntu 20.04, OpenCV 3.5.4, FFmpeg 4.2.4

  


  Im currently reading the output of a cv2.VideoCapture session using the CV_FFMPEG backend and successfully writing that back out in real time to a file using cv2.VideoWriter. The reason I am doing this is to drawing bounding boxes on the input and saving it to a new output.

  


  The problem is I am doing this in a headless environment (Docker container). And I’d like to view what's being written to cv2.VideoWriter in realtime.

  


  I know there are ways to pass my display through using XQuartz for example so I could use cv2.imshow. But what I really want to do is write those frames to an RTSP Server. So not only my host can "watch" but also other hosts could watch too.

  


  After the video is released I can easily stream the video to my RTSP Server using this command.

  


  ffmpeg -re -stream_loop -1 -i output.mp4 -c copy -f rtsp rtsp://rtsp_server_host:8554/stream

  


  Is there anyway to pipe the frames as they come in to the above command ? Can cv2.VideoWriter itself write frames to an RTSP Server ?

  


  Any ideas would be much appreciated ! Thank you.

  


• FFMpeg on docker

  31 mai 2022, par user1765862

  I'm trying to run FFMpegCore library in the docker
Here is my Dockerfile

  


  FROM public.ecr.aws/lambda/dotnet:6 AS base

FROM mcr.microsoft.com/dotnet/sdk:6.0-bullseye-slim as build
WORKDIR /src
COPY ["AWSServerless.csproj", "AWSServerless/"]
RUN dotnet restore "AWSServerless/AWSServerless.csproj"

WORKDIR "/src/AWSServerless"
COPY . .
RUN dotnet build "AWSServerless.csproj" --configuration Release --output /app/build

FROM build AS publish

#fix for using System.Drawing.Common on docker
RUN apt-get update && apt-get install -y apt-utils libgdiplus libc6-dev

RUN apt-get install -y ffmpeg

RUN dotnet publish "AWSServerless.csproj" \
            --configuration Release \ 
            --runtime linux-x64 \
            --self-contained false \ 
            --output /app/publish \
            -p:PublishReadyToRun=true  

FROM base AS final
WORKDIR /var/task

CMD ["AWSServerless::AWSServerless.LambdaEntryPoint::FunctionHandlerAsync"]
COPY --from=publish /app/publish .


  


  When I try to use any of FFMpegCore commands I'm getting following error in the log

  


  


  System.ComponentModel.Win32Exception (2) : An error occurred trying to
start process 'ffmpeg' with working directory '/var/task'. No such
file or directory