Supported Audio Formats in Playback & Recording
July 7, 2009
Supported Audio Playback formats:
- AAC
- HE-AAC
- AMR (Adaptive Multi-Rate, a format for speech)
- ALAC (Apple Lossless)
- iLBC (internet Low Bitrate Codec, another format for speech)
- IMA4 (IMA/ADPCM)
- linear PCM (uncompressed)
- µ-law and a-law
- MP3 (MPEG-1 audio layer 3
Supported Audio Recording Formats:
- ALAC (Apple Lossless)
- iLBC (internet Low Bitrate Codec, for speech)
- IMA/ADPCM (IMA4)
- linear PCM
- µ-law and a-law
AAC, MP3, and ALAC (Apple Lossless) Playback for AAC, MP3, and ALAC sounds can use efficient hardware-based decoding on iPhone OS–based devices, but these codecs all share a single hardware path. The device can play only a single instance of one of these formats at a time through hardware. If the user is playing a sound in one of these three formats in the iPod application, then your application—to play along over that audio—will employ software decoding. AAC, ALAC, MP3 can employ hardware decoding for playback.
Linear PCM and IMA4 (IMA/ADPCM You can play multiple linear PCM or IMA4 sounds simultaneously in iPhone OS without incurring CPU resource problems. It is same for the AMR and iLBC speech-quality formats, and for the µ-law and a-law compressed formats.
The device can play only a single instance of one of these formats at a time through hardware. For example, if you are playing a stereo MP3 sound, a second simultaneous MP3 sound will use software decoding. Similarly, you cannot simultaneously play an AAC and an ALAC sound using hardware. If the iPod application is playing an AAC sound in the background, your application plays AAC, ALAC, and MP3 audio using software decoding.
To play multiple sounds with best performance, or to efficiently play sounds while the iPod is playing in the background, use linear PCM (uncompressed) or IMA4 (compressed) audio.
