title: Download Partial Video via HTTP (for Remote Thumbnailing)
body: <p>I have videos hosted on Amazon S3.  I encode them with Zencoder and store a thumbnail for the video then using Zencoder.  However, I need a way to generate thumbnails at certain points in the video (i.e. 00:00:03, 00:10:32, 01:40:18) and store them either on S3 or my server.</p>
  
  <p>ffmpeg allows remote thumbnailing, however it takes a very long time (sometimes several minutes) to get a thumbnail from the middle of a file--I believe this is because it downloads the entire file up to that point to get the thumbnail.</p>
  
  <p>My plan is to somehow download the header of the video file via HTTP byte-range request, guesstimate the byte range where I should be looking for the thumbnail, download about a second of video from that part of the file via HTTP byte-range request, then save the header and tiny video locally.  I pull the thumbnail from that using ffmpeg and delete the temporary video.</p>
  
  <p>I have no idea on how exactly this would work (I believe the H.264 MP4 files I'm working with have a dynamic length header, for another issue).  <strong>Any suggestions or better ideas?</strong></p>
  
  <p><strong>Edit</strong>: To clarify, Zencoder thumbnailing is great, but they only allow thumbnail creation in combination with transcoding.  I don't want to transcode my video every time I create a new thumbnail, so I need to do this on my own without Zencoder.</p>