Using Go, I take an RTMP stream, transcode it to FLAC (using ffmpeg) and try to pass audio transcription to the Google Speech API. However, I continue to receive EOF errors when sending data. I can’t find the information about this error in the docs, so I'm not quite sure what causes it.
I divide the received data into 3s-clips (the length is not relevant if it is less than the maximum length of the streaming recognition request).
Here is the core of my code:
func main() { done := make(chan os.Signal) received := make(chan []byte) go receive(received) go transcribe(received) signal.Notify(done, os.Interrupt, syscall.SIGTERM) select { case <-done: os.Exit(0) } } func receive(received chan<- []byte) { var b bytes.Buffer stdout := bufio.NewWriter(&b) cmd := exec.Command("ffmpeg", "-i", "rtmp://127.0.0.1:1935/live/key", "-f", "flac", "-ar", "16000", "-") cmd.Stdout = stdout if err := cmd.Start(); err != nil { log.Fatal(err) } duration, _ := time.ParseDuration("3s") ticker := time.NewTicker(duration) for { select { case <-ticker.C: stdout.Flush() log.Printf("Received %d bytes", b.Len()) received <- b.Bytes() b.Reset() } } } func transcribe(received <-chan []byte) { ctx := context.TODO() client, err := speech.NewClient(ctx) if err != nil { log.Fatal(err) } stream, err := client.StreamingRecognize(ctx) if err != nil { log.Fatal(err) } // Send the initial configuration message. if err = stream.Send(&speechpb.StreamingRecognizeRequest{ StreamingRequest: &speechpb.StreamingRecognizeRequest_StreamingConfig{ StreamingConfig: &speechpb.StreamingRecognitionConfig{ Config: &speechpb.RecognitionConfig{ Encoding: speechpb.RecognitionConfig_FLAC, LanguageCode: "en-GB", SampleRateHertz: 16000, }, }, }, }); err != nil { log.Fatal(err) } for { select { case data := <-received: if len(data) > 0 { log.Printf("Sending %d bytes", len(data)) if err := stream.Send(&speechpb.StreamingRecognizeRequest{ StreamingRequest: &speechpb.StreamingRecognizeRequest_AudioContent{ AudioContent: data, }, }); err != nil { log.Printf("Could not send audio: %v", err) } } } } }
Running this code gives the following result:
2017/10/09 16:05:00 Received 191704 bytes 2017/10/09 16:05:00 Saving 191704 bytes 2017/10/09 16:05:00 Sending 191704 bytes 2017/10/09 16:05:00 Could not send audio: EOF 2017/10/09 16:05:03 Received 193192 bytes 2017/10/09 16:05:03 Saving 193192 bytes 2017/10/09 16:05:03 Sending 193192 bytes 2017/10/09 16:05:03 Could not send audio: EOF 2017/10/09 16:05:06 Received 193188 bytes 2017/10/09 16:05:06 Saving 193188 bytes 2017/10/09 16:05:06 Sending 193188 bytes // Notice that this doesn't error 2017/10/09 16:05:09 Received 191704 bytes 2017/10/09 16:05:09 Saving 191704 bytes 2017/10/09 16:05:09 Sending 191704 bytes 2017/10/09 16:05:09 Could not send audio: EOF
Note that not all of Send fail.
Can someone point me in the right direction? Does this have anything to do with FLAC headers or something else? I also wonder, maybe if flushing the buffer discards some data (i.e., this is a non-trivial operation that actually takes some time) and she doesn't like this missing information?
Any help would be really appreciated.