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Convert 2 channel mp4 to each mono wav file using FFMPEG or Python code

I am new to audio files and its codecs.

I would like to convert a 2 channel mp4 file to a single mono wav files.

My understanding is a when I say 2 channel, it stores speech coming from each microphone in a separate channel. And when I split the channels to each individual mono wav files, I get speech of each microphone.

My intension here is to get the speech from each channel and convert them to text. This way I can set the name of the speaker based on channel.

I tried with ffmpeg and python code as well, unfortunately I get two files with same content.

Looking at the following details can someone construct ffmpeg command or python script to convert the 2 channel mp4 file to 2 individual mono wav files.

FFprobe ffprobe -i Two-Channel.mp4 -show_streams -select_streams a

Result

Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    encoder         : Google
  Duration: 00:52:42.19, start: 0.000000, bitrate: 421 kb/s
  Stream #0:0[0x1](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 640x360 [SAR 1:1 DAR 16:9], 322 kb/s, 25 fps, 25 tbr, 12800 tbn (default)
      Metadata:
        handler_name    : ISO Media file produced by Google Inc.
        vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 96 kb/s (default)
      Metadata:
        handler_name    : ISO Media file produced by Google Inc.
        vendor_id       : [0][0][0][0]
[STREAM]
index=1
codec_name=aac
codec_long_name=AAC (Advanced Audio Coding)
profile=LC
codec_type=audio
codec_tag_string=mp4a
codec_tag=0x6134706d
sample_fmt=fltp
sample_rate=44100
channels=2
channel_layout=stereo
bits_per_sample=0
initial_padding=0
id=0x2
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/44100
start_pts=0
start_time=0.000000
duration_ts=139452416
duration=3162.186304
bit_rate=96000
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=136184
nb_read_frames=N/A
nb_read_packets=N/A
extradata_size=16
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
DISPOSITION:non_diegetic=0
DISPOSITION:captions=0
DISPOSITION:descriptions=0
DISPOSITION:metadata=0
DISPOSITION:dependent=0
DISPOSITION:still_image=0
TAG:language=eng
TAG:handler_name=ISO Media file produced by Google Inc.
TAG:vendor_id=[0][0][0][0]
[/STREAM]

FFmpeg command

ffmpeg -i Two-Channel.mp4 -filter_complex "pan=mono|c0=0c0" left_channel.wav

python code using FFPMEG I converted mp4 to wav and then tried below code enter image description here enter image description here

Solution

  • Are you sure that your source file really does have each speaker on a separate channel?

    • you can quickly verify by playing back on headphones and listen to just one side.
    • You could also inspect the source audio with Audacity (free opensource audio editor). This would let you visually see the difference between the channels and also play back each one independently.

    I don't see anything wrong with a cursory look at your ffmpeg command, but I didn't try running it.

    I've used this command to separate audio channels:

    ffmpeg -i Two-Channel.mp4 -map_channel 0.0.0 ch_1.wav -map_channel 0.0.1 ch_2.wav

    It's straight from the ffmpeg wiki