Find out the recorded time of an audio file

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Nikan Fakhari 2022-4-25

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评论： Nikan Fakhari 2022-4-28

Hi There,

I have an .wav audio file which I have recorded and I would like to look into its metadata and extract the

recorded time of this file (e.g., 6:31:12 pm). First I was wondering if this is possible with MATLAB? and if so

could anyone guide me into the right path?

All the best,

Nikan

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Walter Roberson 2022-4-27

id3parse() from the File Exchange assumes ID3v2 tags that are at the very beginning of the file. .WAV files do not support an ID3 tag at the very beginning of the file.

There is no standard for how to insert ID3 tags into WAV files. Two broad classes of work-arounds have been used:

Just add a 'ID3' tag at the very end of the .wav file -- creating something that does not satisfy the defined format of WAV files. You should be able to concatenate .WAV files, so what you see after a valid header and body in a WAV file, if there is anything at all, should be another valid WAV header and so on. It is, though, potentially compatible with ID3v1 tag readers, as those were expected at the end of .MP3 files
Put the ID3 tag inside a WAV LIST chunk. This is compatible with the WAV format, but is not necessarily expected by any media programs

You could potentially modify ID3parse.m to search the content of the input file looking for 'ID3' and trying to read information. Generally speaking, 'ID3' can occur accidentally in audio data, or can occur as part of something like a comment, so the fact that you found 'ID3' does not necessarily mean that what follows is ID3 tags. And given the principle that you can concatenate .wav files, it follows that there could be multiple 'ID3' occurances.

Walter Roberson 2022-4-28

ID3v1 'ID3' chunks were placed at the end of .mp3 files.

ID3v2 'ID3' chunks were placed the the beginning of .mp3 files -- literally as the very first thing in the file.

If you have a .wav file that starts (very first thing) with 'ID3' then it cannot possibly be a valid .wav file.

If you are starting with a .wav file and using id3parse() from the File Exchange on the .wav, then that code will never be able to find ID3 tags in the file, even if they are present.

If you are starting with a .wav file and using some external utility to convert it to .mp3 file, and then using id3parse() from the File Exchange on the .mp3 file, then if the recorded date does not show up, you have several possibilities:

the .wav file might not have that information stored anywhere in any form
the .wav file might not have that information stored in a tag format that the particular conversion utility knows to look for; for example the recording date might be stored as a comment field but the convertor might not think to try to interpret comment fields as potential information to be added to the MP3 tags. That is, this situation covers the case where the information is not written following any of the more common ad-hoc ways of writing tags; it might be difficult to find conversion utilities that match whatever random way the information was written into the .wav file
the .wav file might have the information stored using a different common ad-hoc way than the conversion utility expects, but a different convertor might know about the method (e.g., non-conforming ID3 chunk at the end of the file versus ID3 embedded in a conforming LIST chunk)
the .wav file might (not common!) not have the information stored in the first header + body, as it might happen to consist of several WAV files concatenated together
the .wav file might have it stored using a different identifier than is expected by the conversion program

Thus, the fact that the tag does not show up in a .mp3 file converted from .wav does not necessarily mean that the information was not present in the .wav in any form.... but it might mean that.

That particular information is not information that is commonly stored even with .mp3 files, so it would not be surprising if it does not show up in .wav files.

It might be interesting to run the .wav file through a program such as "Audio File Health Check" which is a MacOS program; https://2manyrobots.com/plaster/

Nikan Fakhari 2022-4-28

Thank you very much for this information. Do you have any idea of the modification that i could apply to the id3pars() function so i could directly look into the tag at the end of the .wav file? potentially all i need right now is to make sure that if my wave file has a recorded date and time associate with it. I would be more than happy to check this with any external software as well does not necessary have to matlab. I know you have included java but i’m not very experienced with that. I would highly appreciate it your help.

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