why does my .amr recording sound stretched, robotic, low pitched

2013-08-10 20:40:37

i have searched everywhere on the internet but not able to identify anyone else having this problem. i have recorded a conversation from my samsung mobile but when i try to playback the .amr file, the recording sounds stretched, very low pitched, robotic manly voice.

i can share the audio file if someone can diagnose the problem and fix it. it is very very important for me because i am going to be recording very important conversations using my phone.

please, please help me out.

thanks.

why does my .amr recording sound stretched, robotic, low pitched

Reply #1 – 2013-08-10 22:47:34

If it's an Android phone, and the future conversations are important, you might prefer something like the AndRecorder app, which can record in PCM audio (uncompressed) for later conversion if you wish (into MP3, Vorbis, AAC, Opus or whatever) or lossless storage (e.g. FLAC). It will operate at 11025, 22050 or 44100 Hz sampling rates in mono on my ancient phone and I use it for recording song ideas from time to time (AMR is not good for musical content). I found that 22050 was more than adequate for high quality conversations. The uncompressed bitrate for mono at 22050Hz, 16-bit is 352.8kbps (159 MB per hour). Double or halve that for 44.1 or 11.025 kHz respectively.

I have been able to play back AMR content in Audacity (imported using FFMPEG libraries), usually from my Android 3GP videos, but I think I was also able to import AMR from Voice Recorder also, but I just tend not to record using Voice Recorder since installing AndRecorder.

why does my .amr recording sound stretched, robotic, low pitched

Reply #2 – 2013-08-11 01:40:44

Much more simply, the problem is probably that you are playing it back at a sampling rate lower than the one at which it was recorded, hence it being slowed down. Does your phone allow you to choose the sampling rate when recording? Which player are you using? Does it allow you to choose the sampling rate for playback? Have you tried any other player(s)?

why does my .amr recording sound stretched, robotic, low pitched

Reply #3 – 2013-08-11 14:05:25

That's a good point. It might be an AMR wideband (16kHz) recording being played back as if it's narrowband (8kHz)