问题
I'm using AVAssetDownloadTask to download some FairPlay-encrypted audio. As per guidelines, the audio is split up into small chunks to allow switching between bitrates during streaming. Our chunks are about 6 seconds each, which means less than 100 kb in size.
The download speed of this process is pretty bad. I've seen speeds between 85 KB/s and 250 KB/s. This is on a connection where when I download a new Xcode beta, I get several megabytes per second.
I'm guessing that the slow speed is due to having to make a separate request for each segment, which is a lot of overhead. I've tried inspecting the download traffic using Charles, and even though it shows one HTTPS connection per download task, the request body size continually ticks upward over the lifetime of the download. I tried downloading a 100MB test file from the same server where the audio files live and it came down at a few megabytes per second.
My question: what are best practices for getting good download performance using AVAssetDownloadTask? Should the segments be larger? Should there be a separate file that is one large chunk for downloading? Or is this behavior weird, suggesting I've got something configured wrong?
来源：https://stackoverflow.com/questions/50455030/download-performance-of-avassetdownloadtask