Setup CDN on DNS


Depending on how much control given to CDN provider, most to least, here are the four config options.
Assumption: we are the video content provider and our server domain name is awsq.MaxxSports.cc
1. Redirect to CDN’s domain name with CNAME
2. Change my DNS so that it uses CDN’s Nameservers to resolve awsq.MaxxSports.cc
3. By A record, let awsq.MaxxSports.cc point to CDN’s IP.
4. Use a separate domain name for CDN access, e.g. d2t4kyunpgtwxc.cloudfront.net

More details for the four options, with the same numbering.
1. we have least control, since all our DNS does is just a redirection. This is the setup of Tencent CDN, like *.cdn.dnsv1.com
2. CDN has much control. For requests of awsq.MaxxSports.cc, CDN decides which IP to resolve to, e.g. depending on each user’s geographic location.
Taking CloudFlare as an example, after login at https://dash.cloudflare.com/login, it asks to update my DNS settng at enom.com with those nameservers: scott.ns.cloudflare.com venus.ns.cloudflare.com
Since multiple domain names could share one CDN’s IP, users can only access http://awsq.MaxxSports.cc by domain name, instead of direct IP.
3. since the A record is maintained at my DNS, namely enom.com, I know the CDN’s IP my domain name is mapped to. This is not good as we loses the ability to dynamically map domain name to different IPs in different country for example.
4. this is the setup we use for our streaming server, e.g. d2t4kyunpgtwxc.cloudfront.net. Requests for awsq.MaxxSports.cc go to our original server, and requests for d2t4kyunpgtwxc.cloudfront.net go to our CDN servers.

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Subtitle Options


There are five places for subtitles, listed innermost layer first.
1. in VCL: Video Coding Layer, as part of the frame video, called hardsub. e.g. by ffmpeg drawtext.
2. in SEI as part of NAL in ES, Network Abstraction Layer, e.g. CEA-708. ffmpeg cannot generate this kind.
3. in track in a video file, e.g. mp4.
ffmpeg -i Party.mp4 -i cap.srt -c:v copy -c:a copy -c:s mov_text -metadata:s:s:0 language=eng PartyCap.mp4
Here is a sample video, playable with vlc, by clicking Menu – Subtitle – Sub Track:
[ http://riowing.net/local/subtitle/track/PartyCap.mp4 ]
4. WebVtt: subtitle in separate file, segmented VTT or not, for both VOD and live.
This sample page is segmented VTT: http://riowing.net/local/subtitle/caption.htm
5. Subtitle as a layer in web page outside video player. e.g. outside JW Player.
This is no longer video technology but HTML

 

PartyCap