Transcode in Memory about ffmpegcore

[Agrejus]

The weird thing is, the code works with this line and no changes var processor = arguments.OutputToFile(@"output_test.mp4"); but var processor = arguments.OutputToPipe(new StreamPipeSink(output)); does not work.

[Agrejus]

Also, when I run FFMpeg using the command line I can convert my files without issue.

Command: ffmpeg -i "input.avi" "output.mp4"

[rosenbjerg]

Is there a reason for not using .FromInputFiles(..).ToOutputFile(..) ?

[Agrejus]

@rosenbjerg I was trying to do everything in memory, reading from a file stream and writing to a memory stream. I do not want to save the output file, I want to send the output stream to another destination, that's why I am opting for a memory stream.

[rosenbjerg]

Okay. What sort of stream are you outputting to?
Have you tried from file to pipe? It seems you are using an input file, from your example

[max619]

@Agrejus Hi, this might be an issue with mp4 container cause it requires seeking when encoding. Try different container, for example mov or webm, as i remember it works with them

[Agrejus]

@rosenbjerg I am trying to output to a MemoryStream. I tried from file to pipe and I get a different error, this time with FFMpeg. I suspect that would work if I could get my parameters correct. Error is:

[mp4 @ 00000234cf5120c0] muxer does not support non seekable output
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
Error initializing output stream 0:0 -- 
[aac @ 00000234cefa7980] Qavg: 10458.081
[aac @ 00000234cefa7980] 2 frames left in the queue on closing

@max619 webm does work! Thank you

[Agrejus]

@rosenbjerg It does work in memory if I output to a webm instead of mp4. I believe we can consider this resolved. Not sure why it says pipe broken for an mp4, but webm works.

[rosenbjerg]

That might be because FFMpeg tries to seek in the stream when using mp4, as Max explains.
From the FFMpeg output you posted, it seems Max was spot on :)
Max is the expert on the piping support in this library. He implemented it

I'll close this issue now that your problem is solved :)

[dev-fatih-erol]

Sorry for raising the issue.
My research took a lot of time. I hope it helps someone.

var source = await _fileService.UploadAsync("videos", request.Video);

            var startTime = TimeSpan.FromSeconds(20);
            var duration = TimeSpan.FromSeconds(10);

            using var outputStream = new MemoryStream();

            await FFMpegArguments.FromUrlInput(new Uri(source), options => options
                    .WithCustomArgument("-ss " + startTime.ToString(@"hh\:mm\:ss"))
                    .WithDuration(duration))
                    .OutputToPipe(new StreamPipeSink(outputStream), options => options
                    .ForceFormat(VideoType.Mp4)
                    .WithCustomArgument("-movflags frag_keyframe+empty_moov"))
                    .ProcessAsynchronously();

            var outputData = outputStream.ToArray();

In detail, the code consists of the following steps:

• The first line calls the "_fileService.UploadAsync" method to upload the video file and assigns the result to the "source" variable.

• The second line assigns the starting time of the segment to the "startTime" variable and the duration of the cut to the "duration" variable.

• The third line creates a "MemoryStream" object which will be used as a memory stream to write the cut video data to.

• On the fourth line, an argument is created using the FFMpegArguments library to mark the video to be cut during the specified start time and duration.

• On the fifth line, the cut video with the specified settings is written to the memory stream using the "OutputToPipe" method.

• On the sixth line, the "ForceFormat" method is called to save the video in the MP4 format, with the "frag_keyframe+empty_moov" properties.

• Finally, the "ProcessAsynchronously" method is used to start the process asynchronously, and the cut video is returned as a byte array using the "outputStream.ToArray()" method.