Subtitle bitrates? at DVinfo.net

Jami Jokinen · May 8th, 2003, 12:26 AM

How much of the DVD's bitrate do subtitle streams use?

Do I have to count them all together even only one is displayed at a time?

Rob Lohman · May 8th, 2003, 05:22 AM

Yes, you have to count EVERYTHING together. The whole package
CANNOT exceed 9.8 mbps. In each package all the video, audo
and subtitle packets will be present. I cannot remember how much
each subtitle track adds (they are basically compressed stills)
but it isn't much. Each dolby audio track (5.1) adds 384 kbps if I am
not mistaken and dts normally stays under the 1 mbps. If you
encode your video at around 5 mbps you should be save to add
a couple of other things

Glen Elliott · May 9th, 2003, 07:43 AM

Why....is 9.8 mb/s the max bitrate DVD players can read?

Dennis Adams · May 10th, 2003, 05:29 PM

<<<-- Originally posted by Glen Elliott : Why....is 9.8 mb/s the max bitrate DVD players can read? -->>>

Correct, set top DVD players, that's the spec. You can actually exceed that for short segments, but it's because it's buffered ahead. Sustained, max is 9.8 mbps. Subtitles need to be counted, but generally take up very little room if they are not animated.

///d@

Glen Elliott · May 11th, 2003, 07:16 PM

So say if I encode at 9.9 mb/s (CBR)...I will definitly run into problems? Will the DVD player be able to read it at all? I'm not planning on trying to encode at anything higher- I'm just curious as to what would happen.

Jeff Donald · May 11th, 2003, 07:24 PM

My software warns me the bit rate is too high. I suspect some players would try to play it and probably freeze, others just wouldn't play. Don't know for sure, I never wanted to waste a disc to find out.

Rob Lohman · May 13th, 2003, 10:28 AM

Glenn,

Do NOT overencode! It might work on your player but
it is simply not garantueed to work. That is what we have
standard for! The standard of DVD just does not allow the
bitrate to go over 9.8 mbps TOP. That's it, case closed.

Stay within the guidelines and you should be safe. Don't add
more problems to the mix!

Oh, we are talking about mbps (megaBITs per second) not
MB (megabytes) per second! Your authoring software and
mpeg2 encoders know how to handle all of this.

Jami Jokinen · May 14th, 2003, 03:45 AM

Does anyone really know the _actual_ subtitle bitrate per used subtitle stream?

"Not much" might become "significant" if you have 8 different subtitle streams.

Dennis Adams · May 14th, 2003, 06:36 AM

<<<-- Originally posted by Jami Jokinen : Does anyone really know the _actual_ subtitle bitrate per used subtitle stream?

"Not much" might become "significant" if you have 8 different subtitle streams. -->>>

It is not a fixed amount, it's based directly on subtitle image complexity and frequency of change. Simple subtitles that come on, stay on long enough to be read, and go away, even time 8, is still (I'm guessing) well under 0.1 mbps.

I suggest you build some subtitles that match what you'll need in your project (a few minutes worth of text changes) and measure the bitrate that you get, then multiple by 8.

For your first disc out of the gate with 8 subtitles, it would be better to error on the safe side, so don't try to max out your bitrate to the full 9.8 mbps.

///d@

Rob Lohman · May 14th, 2003, 10:42 AM

Dennis gives good advise, just try it out and see what you get!

Jami Jokinen · May 15th, 2003, 02:53 AM

Yes, and if it turns out that the guess of "under 0.1 mbps" is three or four times too low, it still way lower than I thought it would be.

So if I play safe and count e.g. 0.3 mbps for total subtitle streams, it still leaves me generous amount of space for video and audio.

Thank you for your help guys.

May 8th, 2003, 12:26 AM	#1
Jami Jokinen Regular Crew Join Date: May 2002 Location: Finland Posts: 103	Subtitle bitrates? How much of the DVD's bitrate do subtitle streams use? Do I have to count them all together even only one is displayed at a time?

May 8th, 2003, 05:22 AM	#2
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	Yes, you have to count EVERYTHING together. The whole package CANNOT exceed 9.8 mbps. In each package all the video, audo and subtitle packets will be present. I cannot remember how much each subtitle track adds (they are basically compressed stills) but it isn't much. Each dolby audio track (5.1) adds 384 kbps if I am not mistaken and dts normally stays under the 1 mbps. If you encode your video at around 5 mbps you should be save to add a couple of other things __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

May 11th, 2003, 07:24 PM	#6
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	My software warns me the bit rate is too high. I suspect some players would try to play it and probably freeze, others just wouldn't play. Don't know for sure, I never wanted to waste a disc to find out. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

May 13th, 2003, 10:28 AM	#7
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	Glenn, Do NOT overencode! It might work on your player but it is simply not garantueed to work. That is what we have standard for! The standard of DVD just does not allow the bitrate to go over 9.8 mbps TOP. That's it, case closed. Stay within the guidelines and you should be safe. Don't add more problems to the mix! Oh, we are talking about mbps (megaBITs per second) not MB (megabytes) per second! Your authoring software and mpeg2 encoders know how to handle all of this. __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

May 14th, 2003, 10:42 AM	#10
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	Dennis gives good advise, just try it out and see what you get! __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

May 9th, 2003, 07:43 AM	#3
Glen Elliott Wrangler Join Date: Apr 2003 Location: Philadelphia, PA Posts: 2,898	Why....is 9.8 mb/s the max bitrate DVD players can read?

May 10th, 2003, 05:29 PM	#4
Dennis Adams Regular Crew Join Date: May 2003 Location: Madison, WI Posts: 123	<<<-- Originally posted by Glen Elliott : Why....is 9.8 mb/s the max bitrate DVD players can read? -->>> Correct, set top DVD players, that's the spec. You can actually exceed that for short segments, but it's because it's buffered ahead. Sustained, max is 9.8 mbps. Subtitles need to be counted, but generally take up very little room if they are not animated. ///d@

May 11th, 2003, 07:16 PM	#5
Glen Elliott Wrangler Join Date: Apr 2003 Location: Philadelphia, PA Posts: 2,898	So say if I encode at 9.9 mb/s (CBR)...I will definitly run into problems? Will the DVD player be able to read it at all? I'm not planning on trying to encode at anything higher- I'm just curious as to what would happen.

May 14th, 2003, 03:45 AM	#8
Jami Jokinen Regular Crew Join Date: May 2002 Location: Finland Posts: 103	Does anyone really know the _actual_ subtitle bitrate per used subtitle stream? "Not much" might become "significant" if you have 8 different subtitle streams.

May 14th, 2003, 06:36 AM	#9
Dennis Adams Regular Crew Join Date: May 2003 Location: Madison, WI Posts: 123	<<<-- Originally posted by Jami Jokinen : Does anyone really know the _actual_ subtitle bitrate per used subtitle stream? "Not much" might become "significant" if you have 8 different subtitle streams. -->>> It is not a fixed amount, it's based directly on subtitle image complexity and frequency of change. Simple subtitles that come on, stay on long enough to be read, and go away, even time 8, is still (I'm guessing) well under 0.1 mbps. I suggest you build some subtitles that match what you'll need in your project (a few minutes worth of text changes) and measure the bitrate that you get, then multiple by 8. For your first disc out of the gate with 8 subtitles, it would be better to error on the safe side, so don't try to max out your bitrate to the full 9.8 mbps. ///d@

May 15th, 2003, 02:53 AM	#11
Jami Jokinen Regular Crew Join Date: May 2002 Location: Finland Posts: 103	Yes, and if it turns out that the guess of "under 0.1 mbps" is three or four times too low, it still way lower than I thought it would be. So if I play safe and count e.g. 0.3 mbps for total subtitle streams, it still leaves me generous amount of space for video and audio. Thank you for your help guys.