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• ffmpeg concat two videos with different sizes encounter "do not match" error

  1 July 2019, by baojieqh

  I’m trying to concat 4 mp4 files. I’m using the command below but not able to concat

  ffmpeg -i L00.mp4 -i L01.mp4 \
  
    -filter_complex "[0:v] [0:a] [1:v] [1:a] concat=n=2:v=1:a=1 [v] [a]" \
  
    -map "[v]" -map "[a]" output.mp4

  Getting this error:

  Input link in1:v0 parameters (size 1150x722, SAR 1:1) do not match the corresponding output link in0:v0 parameters (1158x690, SAR 1:1)

  This command from this post

  ffmpeg -i L00.mp4 -i L01.mp4 -filter_complex \
  
  "[0:v]scale=1158:722:force_original_aspect_ratio=decrease,pad=1158:722:(ow-iw)/2:(oh-ih)/2[v0]; \
  
   [1:v]scale=1158:722:force_original_aspect_ratio=decrease,pad=1158:722:(ow-iw)/2:(oh-ih)/2[v1]; \
  
   [v0][0:a][1:v][1:a]concat=n=2:v=1:a=1[v][a]" \
  
  -map "[v]" -map "[a]" -c:v libx264 -c:a aac -movflags +faststart output.mp4

  getting this error:

  Filter pad has an unconnected output

  the dimensions of L00.mp4 is 1158 × 690, L01.mp4 is 1150 × 722.

  how to fix this?

• Output video file of ffmpeg command video and audio doesn't match

  6 July 2022, by Barry

  i'm trying to trim a video file using ffmpeg using this command
ffmpeg -i input.mp4 -ss 00:05:20 -t 00:10:00 -c:v copy -c:a copy output.mp4 . The problem is when i open the output video, the audio starts normally but the video appears only 5 seconds after. I tried removing the -c copy option and output is accurate but the process is very slow. So my question is how to make output video/audio match when using -c copy option, or how to make the process faster when not using -c copy option. It's my first time using this so i don't know much about video/audio encoding, i am just trying to extract a video clip from a php script.

  


• Open cv.VideoCapture(index) - ffmpeg list camera names - How to match?

  15 November 2024, by Chris P

      def fetch_camera_input_settings(self):
        try:
            self.database_functions = database_functions

            self.camera_input_device_name = database_functions.read_setting("camera_input_device_name")["value"]
            self.camera_input_device_number = int(self.database_functions.read_setting("camera_input_device_number")["value"])

            self.camera_input_devices = [[0,-1,"Καμία συσκευή κάμερας"]]
            self.available_cameras = [{"device_index":-1,"device_name":"Καμία συσκευή κάμερας"}]

            # FFmpeg command to list video capture devices on Windows
            cmd = ["ffmpeg", "-list_devices", "true", "-f", "dshow", "-i", "dummy"]
            result = subprocess.run(cmd, stderr=subprocess.PIPE, stdout=subprocess.PIPE, text=True)
            output = result.stderr  # FFmpeg sends device listing to stderr

            # Updated regular expression to capture both video and audio devices
            device_pattern = re.compile(r'\[dshow @ .+?\] "(.*?)" \(video\)')
            cameras = device_pattern.findall(output)
            counter = 0
            for camera in cameras:
                counter += 1
                self.camera_input_devices.append([counter,counter-1,camera])
                self.available_cameras.append({"device_index": counter-1, "device_name": camera})

            self.to_emitter.send({"type":"available_devices","devices":self.camera_input_devices,"device_index":self.camera_input_device_number})
        except:
            error_message = traceback.format_exc()
            self.to_emitter.send({"type":"error","error_message":error_message})



  


  How to match ffmpeg camera device names output with cv2.VideoCapture which wants camera index as input?