[FFmpeg-user] Command line to show channel label/position

[MrNice]

>> On Jan 28, 2025, at 4:14 PM, MrNice <wxcvbn2006 at iol.ie> wrote:
>>
>> On 28/01/2025 18:26, Carl Zwanzig wrote:
>>> On 1/28/2025 8:18 AM, MrNice wrote:
>>>> have an audio file, with MediaInfo I get
>>>> Audio
>>>> Channel layout                           : L R Ls Rs
>>>>   > ffmpeg -v error -layouts | awk '/quad /{print $2}'
>>>> FL+FR+BL+BR
>>>> What is the correct answer?
>>> Both.
>>> Left, assumed to be front (L) = Front Left (FL)
>>> Left surround/side (Ls) = Back Left (BL)
>>> etc
>>>
>>> (that's part way down the AudioChannelManipulation page, even farther down is a list of the channel names and standard layouts, also in the -layouts output)
>>>
>>> z!
>>>
>>> _______________________________________________
>> Are you sure for good Carl?
>>
>> AFAIK, LS is surround and BL is back/Rear
>>
>> Please look here
>>
>> https://mediaarea.net/AudioChannelLayout
>>
>> They say, depending of standardization;
>> Left Surround = Ls = CL = SL = Ls (MediaInfo name)
>> Right Surround = Rs = CR = SR = Rs (MediaInfo name)
>> Left Rear Surround = Lrs = BL = Lsr = SL = Lb (MediaInfo name)
>> Right Rear Surround = Rrs = BR = Rsr = Rb (MediaInfo name)
>>
> I'm not sure I understand the question, but I believe that "back" channels are only involved if there are more than 5 distinct audio signals plus one low frequency signal. By way of explanation, I believe that 5 distinct audio signals plus one low frequency signal is the configuration commonly referred to as "5.1" audio (front left, front right, center, side left, side right, and low frequency). I don't believe that the term "5.1" when used to describe an audio standard (summarized as the description of speaker locations listed in my previous sentence) specifies any "back' audio signals at all. If you wish to convert 5.1 audio to an audio format having more distinct signals or sends, then I think it is up to you to determine how you would like to distribute the audio signals to make use of the additional available channels. Did I say anything useful, or have I just confused the issue?
>
> LL
>
> _______________________________________________

Thank you for your answer.

The point is that ffmpeg and MediaInfo do not output the same answer for 
the channels positions. Side is not Back particularly in the last 
century with quadrophonic.

Or the information embedded in the file is confusing or one of the two 
programs decipher the embedded info in a wrong way. It could be 
interesting to know what is effectively coded inside the file and as 
well how the 2 programs decipher and output that data to understand the 
difference.

Moreover, to get an accurate knowledge on ffmpeg, it could be 
interesting to copy the table https://mediaarea.net/AudioChannelLayout 
in the ffmpeg documentation and add one column with the corresponding 
ffmpeg output.

MrNice