AVAssetWriter takes a file URL as an argument and writes buffers appended to its AVAssetWriterInput to that file.
AVAssetWriter* assetWriter = [[AVAssetWriter alloc]
initWithURL:[NSURL URLWithString:@"...fileURL..."]
fileType:AVFileTypeMPEG4
error:&error];
If a network URL is specified (i.e. RTSP - a server expecting a live streaming source), an exception is thrown as a file-based URL is required.
Is there another way of accessing the asset writer output? I want to take advantage of the integrated H.264 encoding and just access the encoded data bit by bit to stream it over the network.
No.
Capture the raw samples instead.