Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.

 

Go Back   Doom9's Forum > Video Encoding > MPEG-4 AVC / H.264

Reply
 
Thread Tools Search this Thread Display Modes
Old 4th January 2010, 09:47   #1  |  Link
northerns74r
Registered User
 
Join Date: Dec 2009
Posts: 21
Good picture size compared to bitrate

Hi all,
I am new on this forum and I'd like to ask you a simple thing!
I work for a sort of web-tv. I need to encode several videos recorded and edited in anamorphic PAL definition to the modern standard AVC.

1) I need to limit the bitrate between 1.2-1.5 Mbps.
2) I use x264 (even High 4 profile if I want) for video.
3) I use neroDigital AAC encoder (VBR, 30).

Question:

Do you think in full screen we can achieve better quality resizing the picture to 1024*576 or 720*400?

Consider that videos are quite "static": there are two cameras and we interview people sitting on a radio program, so little moving...

For any question don't wait for asking...

Last edited by Guest; 4th January 2010 at 16:52. Reason: 12
northerns74r is offline   Reply With Quote
Old 4th January 2010, 09:52   #2  |  Link
Dark Shikari
x264 developer
 
Dark Shikari's Avatar
 
Join Date: Sep 2005
Posts: 8,688
1) Don't encode in bitrate mode. You'll often find that videos need far less bitrate than you think they do, which will save you a lot of bandwidth. If you need to limit the overall bitrate, run a two-pass CRF encode; use quality mode on the first pass and limit the bitrate on the second pass. If you need to limit the local bitrate, use VBV.

2) For a low-motion video, higher resolution is practically always better. You don't need more than a few hundred kilobits for that sort of thing at SD resolutions.
Dark Shikari is offline   Reply With Quote
Old 4th January 2010, 10:33   #3  |  Link
northerns74r
Registered User
 
Join Date: Dec 2009
Posts: 21
Thank you for your quick reply.
One thing more: as I use MediaCoder, how can I set quality/bitrate mode for each pass?
The software let me choose four options:
Bitrate/Quality/TwoPass/ThreePass.
I think TwoPass option automatically include the process your were talking about... right?
northerns74r is offline   Reply With Quote
Old 4th January 2010, 12:29   #4  |  Link
LoRd_MuldeR
Software Developer
 
LoRd_MuldeR's Avatar
 
Join Date: Jun 2005
Location: Last House on Slunk Street
Posts: 13,229
You would only use 2-Pass mode to hit a target (average bitrate). For quality-based encoding, you should use 1-Pass CRF mode.

Once you have found the highest possible CRF value that still gives acceptable quality for your eyes (I recommend you start at ~20), you can use that CRF value for all future encodes.

And if you need to limit the "local" bitrate (usually only needed for hardware decoders) you can use CRF+VBV. Note that VBV needs both, a BufSize and a MaxRate.
__________________
There was of course no way of knowing whether you were being watched at any given moment.
How often, or on what system, the Thought Police plugged in on any individual wire was guesswork.


LoRd_MuldeR is offline   Reply With Quote
Old 4th January 2010, 14:23   #5  |  Link
northerns74r
Registered User
 
Join Date: Dec 2009
Posts: 21
So... correct me if I am wrong:

1) As the videos have to be watched in a youtube-like player it would be reasonable that the peak-rate isn't too high... I'd say 1Mbps with peak around 1.5Mbps. Considering the resolution (1024*576) and the low-complexity contents we should achieve a good compromise.

2) The best workflow is to encode each DV.AVI (Anamorphic PAL) exported from Premiere/FinalCut in mp4 (x264/AAC) by two different passes encode. First pass should be a quality based mode (actually CRF) while the second one should be a VBV mode, so that we could control min/max rates "jumps".

3) THE REAL QUESTION: How could I set all of this in MediaCoder. My target is to prepare an export preset to share with other people and be sure all of them send video contents in the same correct way.

Thank you in advance
northerns74r is offline   Reply With Quote
Old 4th January 2010, 14:37   #6  |  Link
LoRd_MuldeR
Software Developer
 
LoRd_MuldeR's Avatar
 
Join Date: Jun 2005
Location: Last House on Slunk Street
Posts: 13,229
1) If your video is intended for streaming, what you need is VBV. The VBV MaxRate is then defined by your network bandwidth, the VBV BufSize by the client's buffer. You can still use CRF mode!

2) Nope. CRF doesn't need two passes! And it (usually) isn't used for the first pass of a 2-Pass encode either. VBV works perfectly fine with 1-Pass CRF. 2-Pass is intended to hit a specific average bitrate (or file size). Unless you need to hit a specific file size, 2-Pass won't be needed. What you want is a VBV-restricted and quality-based 1-Pass encode. That is: CRF mode + VBV.

3) Don't ask me. Use x264 from the command-line (it really isn't that hard!) or use a GUI that lets you set all the required options. I have no idea about the MediaCoder front-end
__________________
There was of course no way of knowing whether you were being watched at any given moment.
How often, or on what system, the Thought Police plugged in on any individual wire was guesswork.



Last edited by LoRd_MuldeR; 4th January 2010 at 14:52.
LoRd_MuldeR is offline   Reply With Quote
Old 4th January 2010, 16:07   #7  |  Link
AnonCrow
Registered User
 
Join Date: Aug 2009
Location: 61.45 , 23.86
Posts: 120
Quote:
Originally Posted by northerns74r View Post
3) THE REAL QUESTION: How could I set all of this in MediaCoder. My target is to prepare an export preset to share with other people and be sure all of them send video contents in the same correct way.
Click the Encoder button on the video tab to open x264 extended settings. The two VBV settings are ~20 options down. After successfully testing that certain settings work and provide acceptable quality: File -> Save as Preset
Assuming all people use the same build of Mediacoder, share the preset XML file with them. After adding a file to Mediacoder, right click on one file (or select all , ctrl-A) , Set Preset File.

Though it possible that if you choose a high enough CRF and a slow enough x264 preset, VBV settings won't even be needed.
AnonCrow is offline   Reply With Quote
Old 4th January 2010, 18:22   #8  |  Link
Dark Shikari
x264 developer
 
Dark Shikari's Avatar
 
Join Date: Sep 2005
Posts: 8,688
Quote:
Originally Posted by northerns74r View Post
So... correct me if I am wrong:

1) As the videos have to be watched in a youtube-like player it would be reasonable that the peak-rate isn't too high... I'd say 1Mbps with peak around 1.5Mbps. Considering the resolution (1024*576) and the low-complexity contents we should achieve a good compromise.

2) The best workflow is to encode each DV.AVI (Anamorphic PAL) exported from Premiere/FinalCut in mp4 (x264/AAC) by two different passes encode. First pass should be a quality based mode (actually CRF) while the second one should be a VBV mode, so that we could control min/max rates "jumps".

3) THE REAL QUESTION: How could I set all of this in MediaCoder. My target is to prepare an export preset to share with other people and be sure all of them send video contents in the same correct way.

Thank you in advance
I would strongly recommend against using MediaCoder for this purpose. For that matter, using it for any purpose at all.
Dark Shikari is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 07:14.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.