Determine the duration of an mp3 file

[SzymonWojd]

Hi, is there any way to determine the duration in seconds of an mp3 file using this library? Also, I would be grateful if you could help me with checking how much time is left to the end of a playing file. I am building A2DP audio player which streams mp3 files and this information would be really helpful for me.

[pschatzmann]

For the first question: google is your friend!

For the second: just read the actual file position and compare it with the total file size

[SzymonWojd]

Thank you for the answer. How can I read the actual file position? Is there a function in your library that does that?

[pschatzmann]

The AudioPlayer provides you a pointer to the actual stream.: In your case this is a pointer to a File, so you can just cast it to (File*).

[SzymonWojd]

I wrote this lines of code:
File pFile = (File)player.getStream();
Serial.println(pFile->position());
However when I try to run the code my ESP32 just keeps resetting. Do you know what might be a problem?

[pschatzmann]

It should be
File* pFile = (File*)player.getStream();
And before using it, you must make sure that it is not nullptr!

[pschatzmann]

The MP3DecoderHelix provides the audioInfoEx() method which return a MP3FrameInfo struct that contains the bitrate.

[varungujjar]

Thankyou @pschatzmann for such a quick response, sorry but I am little new to this and I am getting the following
44,100 Khz / 16 Bit / 2 Channels and calculate using a forumla 44100*16 *2 = 1, 411 Kbps, but is there a way to get the actual bit rate such as 128kbps, 192Kbps etc. ?

[hash6iron]

Hello @pschatzmann

Yes, the bitrate could be consulted in audioInfoEx() from decoder, but I've observed that VBR MP3 don't play correctly when bitrate is consulted each time. Is there any solution to calculate duration for a variable bit rate MP3 avoiding playing issues?

Thanks for all.

[pschatzmann]

Why would you do something like this ? You would do this only once to get a rough first estimate (if ever).
You can use the MeasuringStream to estimate the total runime or the time left using the approach described in my first answer:

• calling begin records the start time
• putting it into the chain or calling setProcessedBytes() with the actual file position records the progress
• estimatedOpenTimeFor(file size) gives the remaining time
• estimatedTotalTimeFor(file size) give the updated total time

[pschatzmann]

I have added an example to the documentation