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Old 11-02-2012, 02:24 AM   #1
Registered: May 2010
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ffmpeg mpeg2 encoding bottleneck, and I can't find a work around.

I noticed on my quad core machine that ffmpeg would not use more than 50% on each core.

#First I created a ramdisk with lilo using append=" ramdisk_size=4194304"
#On fstab I added the line:
/dev/ram0 /ram tmpfs defaults 1 2

#then ran lilo
#created the /ram directory

#after the reboot with the ram disk I clocked up my cpu to its full clock of 1600Mhz per core, using cpufreq-set.

branden 3433 179 0.2 266920 15316 pts/0 Sl+ 01:12 1:15 ffmpeg -threads 8 -i dex.mpg -an -vcodec mpeg2video -threads 8 -b 15000k dex.mpeg

ffmpeg -threads 8 -i dex.mpg -an -vcodec mpeg2video -threads 8 -b 15000k dex.mpeg

frame=72058 fps=505 q=2.0 Lsize= 471050kB time=00:50:02.37 bitrate=1285.3kbits/s

Any clue why ffmpeg won't use more than 50% cpu on ram disk or hard disk, or a work around?

bash-4.2$ x262 --mpeg2 -B 15000 -o dex.mpeg dex.mpg
[mpeg @ 0x12032a0] max_analyze_duration 5000000 reached at 5000000
lavf [info]: 480x272p 136:135 @ 24/1 fps (vfr)
x262 [warning]: MPEG-2 + VFR is not allowed
x262 [warning]: invalid display aspect ratio
x262 [info]: using SAR=1/1
x262 [info]: using cpu capabilities: MMX2 SSE2Fast FastShuffle SSEMisalign LZCNT
x262 [info]: Main profile @ Main level
10970 frames: 258.78 fps, 533462.64 kb/s

It is slow but encodes using all of the cpu. Well it seems to affect x262 as well.

Last edited by darkstarbyte; 11-02-2012 at 02:49 AM. Reason: add x262 stuff
Old 11-02-2012, 09:44 PM   #2
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frame=72058 fps=505 q=2.0 Lsize= 471050kB time=00:50:02.37 bitrate=1285.3kbits/s
505 frames per second with a quality of 2 is blazing fast encoding with ffmpeg.
I don't know why all 4 cores aren't hitting 100%, but that's not slow.

8 threads with 4 cores, I never specify that, ffmpeg multi threads by default.
-b 15000k that's a huge video bitrate, it'll give you a huge file with no difference in video quality. I use 2500k sometimes with 1 pass encoding and that is quite big.

I've read of others speaking of this.
Old 11-03-2012, 06:17 AM   #3
Registered: May 2010
Location: 3 planets away from the sun.
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It does not even use 15000k, I just used that so it could go faster, but that did not help.

Before and after the encode, because I encoded it to mpeg2 and I wanted to see why mpeg2 to mpeg2 was so slow also. On my mono-core pentium 4 clocked at 3.06Ghz I still get around 200fps.

Video Spec:
Stream #0:0(und): Video: mpeg2video, yuv420p, 480x272 [SAR 161:160 DAR 483:272], q=2-31, 15000 kb/s, 90k tbn, 24 tbc

I am building ffmpeg from scratch with custom CFLAGS, and I hope that will solve some of the issue.

Last edited by darkstarbyte; 11-03-2012 at 06:25 AM.


bottleneck, ffmpeg, mpeg

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