Using pipes result in immediate call of .complete callback

[ggschelling]

Hi there,

I'm using 2 pipes as input (video and audio). Everything looks good until ffmpeg-kit initialized. Then the .complete callback gets called immediately. Changing these inputs to a public url (e.g. https://........mp4), everything works fine. Hopefully, someone could help me with this issue or point me in the right direction.

Some more details:
I'm using a broadcast extension on iOS, which provide me with uncompressed CMSampleBuffers. These get appended in 2 different AVAssetWriter objects (audio and video). After encoding, AVAssetWriterDelegate gets called. There I get Data packages which will be written into the video and audio pipes. This is working nicely for a few seconds until a sufficient buffer is build and ffmpeg-kit gets initialized. As an output, I defined a TCP connection to my MacBook where ffplay is waiting for input. Ffplay opens a window and plays the encoded video and audio. Then the mentioned .complete callback gets called and stops sending data to ffplay.

I can't tell what the problem is. It somehow seems that ffplay-kit is done working and triggers completion. Maybe it's done reading the file up until the current status. But it should continue read data from the pipes and forward it to the tcp connection.

Any idea? I do appreciate any help/hints! Thx in advance 🙏

Code:

Here I get the video and audio Data packets:

extension SampleHandler: AVAssetWriterDelegate {
    func assetWriter(_ writer: AVAssetWriter, didOutputSegmentData segmentData: Data, segmentType: AVAssetSegmentType, segmentReport: AVAssetSegmentReport?) {
        let isVideo = (writer == videoWriter)
        if isVideo {
            videoDataCounter += 1
        } else {
            audioDataCounter += 1
        }
        
        writeQueue.sync {
            self.writeSegmentDataToPipe(segmentData, isVideo: isVideo)
        }
    }
}

Build a buffer to not loose any packets during initialization:

func writeSegmentDataToPipe(_ data: Data, isVideo: Bool) {

        var hTempSegmentBuffer = isVideo ? tempSegmentBuffer : audioTempSegmentBuffer
        let hFfmpegPipeWriteHandle = isVideo ? ffmpegPipeWriteHandle : audioFfmpegPipeWriteHandle
        
        // Store data in buffer
        hTempSegmentBuffer.append(data)
        
        do {
            guard let fileHandle = hFfmpegPipeWriteHandle else {
                print("warn: video write file handle is not initialized")
                return
            }
            if !hTempSegmentBuffer.isEmpty {
                try fileHandle.write(contentsOf: hTempSegmentBuffer.first!)
                hTempSegmentBuffer.removeFirst()
            }
        } catch {
            print("error: writing segment data to pipe failed, reason: \(error.localizedDescription)")
        }
    }

Initialization of ffmpeg command:

let input = "-y -i " + pipeURL.path + " -use_wallclock_as_timestamps 1 -i " + audioPipeURL.path
var arguments = [String]()
arguments.append("-thread_queue_size 50k")
arguments.append("-analyzeduration 10k")
arguments.append("-probesize 150k")
arguments.append("-c:v copy")
arguments.append("-c:a copy")
arguments.append("-f matroska")
arguments.append("-movflags faststart")
arguments.append("tcp://\(ipAddress):\(port)?tcp_noderelay=1")
let command = arguments.joined(separator: " ")
FFmpegKit.executeAsync(command, withCompleteCallback: { ffSession in
   // 💥 ... called completion too early 
}