I'm doing some experiments with video streaming from and the front camera of the android device to a local server. Currently I plan to use WiFi. I may move to Bluetooth 4.0 in the future.
I'm looking for insights, experience and DOs and DON'Ts and other ideas that I should consider in relation to protocol options (TCP, UDP, ...? ) and video codec. The image quality should be good enough to run computer vision algorithms such as face and object detection, recognition and tracking on the server side. The biggest concern is power. I want to make sure that the streaming is as power efficient as possible. I understand more power efficiency means a lower frame rate.
Also, I need to way to just send the video frames without displaying them directly on the screen.
Thanks.
You didn't mention whether you will be doing encoding or decoding on the device.
Some tips: UDP will be less power hungry in general especially under deteriorating network conditions: See http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.134.5517&rep=rep1&type=pdf Check for more papers on this on google
In terms of codecs in general you can say the order is H264 > MPEG4 > H.263 in terms of power needed for both encoding and decoding.
Higher the bitrate more the power needed for decoding but the codec difference is a bigger difference than the bitrate one. I say this because to get same quality as a H.264 stream with H.263 you need higher bitrate. But h.263 at that bitrate should consume lesser power than H.264 at the lower bitrate. So do not apply it cross codec. Just at the codec chosen use the lowest bitrate/framerate you can.
In encoding though very low bitrates can make the encoder work harder so increase power consumption. So encoding bitrates should be low, but not so low that the encoder is streched. This means choosing a reasonable bitrate which does not produce a continous blocky stream but gives a decent stream output.
Within each codec if you can control the encoding then you can also control the decoding power. The following applies to both: i.e. Deblocking, B Pictures will add to power requirements. Keeping to lower profiles [Baseline for H.264, Simple Profile for MPEG4 and Baseline for H.263] will result in lesser power requirements in encoding and decoding. In MPEG4 switch off 4MV support if you can. Makes streams even simpler to decode. Remember each of these also have a quality impact so you have to find what is acceptable quality.
Also unless you can really measure the power consumption I am not sure you need very fine tweaking of the toolsets. Just sticking to the lower profiles should suffice.
Worse the video quality during capture more the power needed during encoding. So bright lighted videos need lesser effort to encode, low light videos need more power.
There is no need to send videos to a screen. you receive video over a socket and do whatever you want to do with that data. That is upto you. You do not have to decode and display it.
EDIT: Adding a few more things I could think off
In general the choice of codec and its profile will be the biggest thing affecting a video encoding/decoding system's power consumption.
The biggest difference may come from the device configuration. If you have hardware accelerators for a particular codec in the device it may be cheaper to use those than software codec for another one. So though H.264 may require more power than MPEG4 when both are in software, if the device has H.264 in hardware then it may be cheaper than MPEG4 in software. So check you device hardware capability.
Also video resolution matters. Smaller videos are cheaper to encode. You can clock your device at lower speeds when running smaller resolutions.