Closed ericoporto closed 2 years ago
This is easy done. Use drmp3_get_pcm_frame_count()
and derive it from the sample rate:
lengthInSeconds = drmp3_get_pcm_frame_count(&mp3) / mp3.sampleRate;
The example above calculates the length in seconds. From there it's a trivial conversion to milliseconds. The sample rate can be retrieved directly from the drmp3
struct.
I saw two additional cases, one in al_mp3, where is looks like a header exists with the information ready in xing header. The other is a case where it's a variable rate but this header it seems is not available or the person was not aware, which is reported here https://github.com/lieff/minimp3/issues/54. I was just looking for a method that could check all of these and give me the direct answer.
So dr_mp3 will always iterate over the entire file like in that minimp3 issue you mentioned. That will give you an accurate frame count, but it comes at the expense of a slow processing time. There's no header interrogation going on in dr_mp3, though I would like to support that eventually.
Another potential issue is when the sample rate changes between MP3 frames. The sample rate used by dr_mp3 is always the sample rate of the first MP3 frame. I think this is quite uncommon though? Regardless, I have little interest in supporting that scenario.
Thanks for the information. :)
I could not figure how to get the length of the mp3 in ms, if this is already supported, disregard this. But if not, I think this is a new feature.