My problem is that I am trying to use ffmpeg to download / extract the nearest keyframe to a timestamp, but I need this without complete download of the file.
I have seen ffmpeg does use content-range but there is something I do not understand

ffmpeg -y -discard nokey -i "http://devimages.apple.com/iphone/samples/bipbop/gear1/fileSequence1.ts" -t 2 -vframes 1 -vsync 0 -update 1 -filter:v select="eq(pict_type\,PICT_TYPE_I)" frame.jpg
If I do the above, I see a very inefficient requests sequence in Wireshark / Charles

[Attachment 54526 - Click to enlarge]

1. content-range 0-262823/262824
2. content-range 12824-262823/262824
3. content-range 0-262823/262824

The file itself has 262824 bytes on disk