-maxrate and -bufsize settings for streaming off USB with hardware decoder?

Shaocaholica · 31st March 2014, 23:17

I'm running some tests for streaming 4k@24fps H.264 video off of a USB2 drive and being decoded by a hardware decoder that can handle (on paper) 120,000kbit max. To give myself some headroom I'm setting -maxrate to 95,000k (which is already pretty damn high) but I'm not sure what I should use for -bufsize given that I'll be streaming from USB. Is there some good method to derive -bufsize given my maxrate and interface practical rate (USB2, ~280,000k real world max).

Right now I'm just playing with:

-maxrate 95000k -bufsize 150000k

Asmodian · 1st April 2014, 05:03

I would think -bufsize should be set based on your desired startup time and/or memory available in the hardware decoder? As I understand VBV it is only -maxrate that would be influenced by the USB2 speed.

Blue_MiSfit · 1st April 2014, 06:28

The general best practice is to use at least a second of buffer - ideally more. Some situations require much less - like low latency scenarios and picky hardware, but you can usually get away with a second or two.

More than 2-3 seconds is diminishing returns in most cases IMO.

31st March 2014, 23:17	#1 \| Link
Shaocaholica Registered User Join Date: Oct 2005 Posts: 19	-maxrate and -bufsize settings for streaming off USB with hardware decoder? I'm running some tests for streaming 4k@24fps H.264 video off of a USB2 drive and being decoded by a hardware decoder that can handle (on paper) 120,000kbit max. To give myself some headroom I'm setting -maxrate to 95,000k (which is already pretty damn high) but I'm not sure what I should use for -bufsize given that I'll be streaming from USB. Is there some good method to derive -bufsize given my maxrate and interface practical rate (USB2, ~280,000k real world max). Right now I'm just playing with: -maxrate 95000k -bufsize 150000k Last edited by Shaocaholica; 31st March 2014 at 23:22.

1st April 2014, 06:28	#3 \| Link
Blue_MiSfit Derek Prestegard IRL Join Date: Nov 2003 Location: Los Angeles Posts: 5,989	The general best practice is to use at least a second of buffer - ideally more. Some situations require much less - like low latency scenarios and picky hardware, but you can usually get away with a second or two. More than 2-3 seconds is diminishing returns in most cases IMO. __________________ These are all my personal statements, not those of my employer :)

1st April 2014, 05:03	#2 \| Link
Asmodian Registered User Join Date: Feb 2002 Location: San Jose, California Posts: 4,407	I would think -bufsize should be set based on your desired startup time and/or memory available in the hardware decoder? As I understand VBV it is only -maxrate that would be influenced by the USB2 speed.