There is a signal processor in the iPhone 4 A5. Phil Schiller mentioned it briefly in the keynote when talking about the camera (64 mins in).
Schiller referred to it as an "Image Signal Processor" so it may be that it is custom silicone for used only by the camera but it seems more likely that it is a more general DSP and was badged like this for the presentation.
It is probably a version of ARM's NEON technology:
NEON technology can accelerate multimedia and signal
processing algorithms such as video encode/decode, 2D/3D
graphics, gaming, audio and speech processing, image
processing, telephony, and sound synthesis by at least
3x the performance of ARMv5 and at least 2x the
performance of ARMv6 SIMD
Which directly mentions both image processing and speech processing.
Update: According to wikipedia that's exactly what it is:
The A5 contains a rendition of chip based upon the
dual-core ARM Cortex-A9 MPCore CPU with NEON SIMD
accelerator and a dual core PowerVR SGX543MP2 GPU.
Interestingly, as this is the iPad A5 being discussed it strengthens the argument for Siri-on-iPad2 (assuming the signal processor is key to Siri working efficiently).
Schiller referred to it as an "Image Signal Processor" so it may be that it is custom silicone for used only by the camera but it seems more likely that it is a more general DSP and was badged like this for the presentation.
It is probably a version of ARM's NEON technology:
http://www.arm.com/products/processors/technologies/neon.php
Which directly mentions both image processing and speech processing.Update: According to wikipedia that's exactly what it is:
http://en.wikipedia.org/wiki/Apple_A5
Their source is the reliable AnandTech:http://www.anandtech.com/show/4216/apple-ipad-2-gpu-performa...
Also, the corresponding A4 page makes no mention of NEON or DSP:
http://en.wikipedia.org/wiki/Apple_A4
Interestingly, as this is the iPad A5 being discussed it strengthens the argument for Siri-on-iPad2 (assuming the signal processor is key to Siri working efficiently).