[MEncoder-users] Fast FLV encoding options

[Eric Laurent]

----- Original Message ----- 
From: "Rich Felker" <dalias at aerifal.cx>
To: "MEncoder usage discussions" <mencoder-users at mplayerhq.hu>
Sent: Saturday, October 06, 2007 7:37 AM
Subject: Re: [MEncoder-users] Fast FLV encoding options


> On Fri, Oct 05, 2007 at 09:54:34PM -0700, RC wrote:
>> On Fri, 05 Oct 2007 17:21:34 -0500
>> James Hastings-Trew <jimht at shaw.ca> wrote:
>>
>> > I find the basic encoding options embodied in the following command
>> > line  work well for one pass encodes as a fairly good clip on my
>> > machine:
>> >
>> > mencoder INPUT -o OUTPUT -of avi -ffourcc DIVX -oac mp3lame -lameopts
>> > br=160:cbr:mode=0
>> > -ovc lavc -lavcopts
>> > vcodec=mpeg4:mbd=2:trell=yes:vbitrate=1600:vrc_maxrate=5000:vrc_buf_s
>> > ize=1835:threads=THREADS
>>
>> I really wouldn't recomend using a bitrate with single-pass encoding.
>> Using a vqscale setting ensures that a complex scene won't turn the
>> video into a mess of artifacts.
>
> vqscale will end up wasting lots of bits on complex scenes and
> producing a bitstream that requires way too much cpu power to decode.
> Reasonable bitrate constraints can give acceptable results in
> single-pass. The problem is what happens if you don't have proper
> constraints and a long complex scene eats all the bits, then lavc
> makes subsequent simple scenes look like crap trying to recover from
> its excessive bit usage...
>
> Rich

Given the quality of the source video I have to handle and the target output 
quality and bitrate, the following methods give roughly the same process 
time and output quality:

1:  vcodec=flv:keyint=4:vqscale=7 -ofps 20

2: 
vcodec=flv:keyint=4:vbitrate=450:vrc_maxrate=1000:vrc_buf_size=1835:threads=1 
 -ofps 20



One advantage of method 1 is that the output bitrate remains "proportional" 
to input bitrate, whereas method 2 tends to produce bigger files for the 
video samples I have tested for non obvious quality improvements.



One remark: the -threads option does not work for flv codec:

# [flv @ 0x87667b0]multi threaded encoding not supported by codec



Eric.