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• FFmpeg pan filter error when routing stereo audio to rear channels of 5.1 output

  13 avril, par MilkyTech

  I'm trying to mix a stereo commentary track into the rear surround channels of a 5.1 audio stream using FFmpeg on Windows 10. My goal is to lower the volume of the original 5.1 movie audio, then add the stereo commentary so it plays from the rear left and right speakers (SL and SR).

  


  I've already converted the commentary to EAC3 to match the main track's codec :

  


  ffmpeg -i "CastCommentary.m4a" -c:a eac3 -b:a 640k CastCommentary.eac3

  


  Then I tried mixing them like this (from within Command Prompt, not PowerShell or a batch file) :

  


  ffmpeg -i "Tropic.Thunder.2008.UNRATED.mkv" -i "CastCommentary.eac3" -filter_complex "[0:a:0]volume=0.4[aud1]; [1:a:0]pan=5.1:FL=0:FR=0:FC=0:LFE=0:SL=c0:SR=c1[cm_rear]; [aud1][cm_rear]amix=inputs=2[aout]" -map 0:v -map "[aout]" -map 0:s? -t 600 -c:v copy -c:s copy -c:a eac3 -b:a 640k "Tropic.Thunder.5.1.commentary.test.mkv"


  


  But I keep getting errors like :

  


  [fc#0 @ ...] Error applying option 'SL' to filter 'pan': Option not found
Error : Option not found


  


  Or :

  


  [Parsed_pan_1 @ ...] Expected in channel name, got ""


  


  Or even :

  


  Output channel layout 5.1 does not match the number of channels mapped 2.


  


  I’ve tried variations of the pan syntax :

  


  

  • pan=5.1:FL=0:FR=0:FC=0:LFE=0:SL=c0:SR=c1

  


  • pan=5.1|FL=0|FR=0|FC=0|LFE=0|SL=c0|SR=c1

  


  • Wrapping in single/double

  


  • quotes Escaping for CMD (no caret issues in current runs)

  


  


  Nothing seems to work.

  


  🎯 Goal :

  


  

  • Keep 5.1 audio from the original movie (volume lowered)

  


  • Add stereo commentary to SL and SR

  


  • Output a proper 5.1 EAC3 mix

  


  


  🔧 System :

  


  

  • Windows 10

  


  • FFmpeg version : [latest static build from ffmpeg.org]

  


  • Running in true Command Prompt (not PowerShell)

  


  • Source audio : 5.1 EAC3 from a .mkv, stereo .eac3 from .m4a

  


  


  What’s the correct filter_complex syntax to route a stereo track to the rear channels of a 5.1 layout using FFmpeg on Windows ? Am I missing something about pan, amix, or Windows quirks ?

  


• Revision 34537 : un pour englober le contenu principal de ...

  17 janvier 2010, par cedric@… — Log

  un pour englober le contenu principal de chaque objet. Permet de cibler le debut ou la fin du contenu principal, ou, en passant par le parent, la fin du contenu.

• Decoding the h.264 stream from a COM port

  18 mars, par Peter

  I would like to know if there is a reliable way to decode an H.264 NAL stream coming through a serial port using software.

  


  So far, I have managed to decode a single frame using a python script. In this script, I first write the incoming data to a file, and when the end-of-frame marker 00_00_00_01 appears, I display the frame using ffplay.

  


  import serial
import subprocess
import os
import time

ser = serial.Serial('COM3', 115200, timeout=1)
output_file = "output.264"

# Variable to store the ffplay process
ffplay_process = None

# Open the file for writing in binary mode
with open(output_file, "wb") as file:

    print("Writing bytes to output.264. Waiting for the end-of-frame marker 0x00000001.")

    buffer = bytearray()
    marker = b'\x00\x00\x00\x01'

    try:
        while True:
            if ser.in_waiting:  # If there is data in the buffer
                data = ser.read(ser.in_waiting)  # Read all available bytes
                buffer.extend(data)

                # Check if the end-of-frame marker is in the buffer
                while marker in buffer:
                    index = buffer.index(marker) + len(marker)  # Position after the marker
                    frame = buffer[:index]  # Extract the frame
                    buffer = buffer[index:]  # Keep the remaining data

                    print(f"Frame recorded: {len(frame)} bytes")
                    file.write(frame)  # Write the frame to the file
                    file.flush()  # Force writing to disk

                    # Close the ffplay window if it is already open
                    if ffplay_process and ffplay_process.poll() is None:
                        ffplay_process.terminate()
                        ffplay_process.wait()  # Wait for the process to terminate

                    # Play the recorded frame, reopening the window
                    ffplay_process = subprocess.Popen(["ffplay", "-f", "h264", "-i", output_file])

    except KeyboardInterrupt:
        print("\nRecording stopped.")
    finally:
        # Close the serial port and the ffplay process
        ser.close()


  


  However, each time a new end-of-frame marker is detected, the ffplay window closes and reopens to show the next frame. It will flicker when transferring the video. Is there a way to display the frames in the same window for seamless playback when streaming video ?

  


  Or is there a better approach or software that is more suited for this task ? I do not know where to start, so I will be glad for any hints.