Hi,
I've been tasked with building an app that receives video from a device over RTSP. The device is a security camera that has a built-in Wifi hotspot. Both the camera and the app are intended to be used in a setting where internet access won't be available, so the app has to communicate directly with the camera. Also, I know that the device transmits an h.264 video stream, which should be compatible with iOS.
The app I'm required to build has to do more than just display a live picture from the camera -- it must also be able to record video to a file, possibly with transcoding to a lower bitrate.
As best I could determine, there isn't anything in AVFoundation or iOS that can directly help me connect to an RTSP server. (If I'm wrong about this, I would love to know about it).
I found some example code on the internet that uses the ffmpeg library as a starting point. I was able to construct a crude video player out of the ffmpeg functions, but it leaves plenty to be desired. In a nutshell, here's what I'm doing:
1. Establish a connection to the RTSP server. This is easily done by passing an RTSP URL to ffmpeg's avformat_open_input function.
2. Try to read a packet. If successful, I append the packet to a frame. If not successful, I wait about 10ms and try again. (This is ugly, but if I do it off the main thread, it seems to be practical).
3. After appending one or more packets to a frame, I get a completed frame that can then be converted to an RGB image by calling the sws_scale function in the ffmpeg library. Then the RGB image can be converted to a CGImageRef and finally a UIImage that is able to be displayed.
Step 3 is really just a test so I can see what the camera is sending and verify that the app is actually receiving video. It is, but the conversion of the frames into UIImages is so CPU-intensive as to be impractical. I'm pretty sure that what I need to do instead is take the packet data from step 2 and generate some sort of an AVAsset out of it, so that AVFoundation can take over from there and give me something that I can play in a standard media player, or stream out to a file.
Should this be possible? Will it be relatively easy, meaning will AVFoundation be able to deal directly with the data from the camera, or will it require a complex transformation? I'm not even sure which AVFoundation objects I should be looking at to do this (assets, tracks, etc).
I'd appreciate any feedback or advice.
Thanks,
Frank
