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Re: high quality videos with idlffvideowrite? [message #84006 is a reply to message #84005] Wed, 24 April 2013 15:42 Go to previous messageGo to previous message
AndrewM is currently offline  AndrewM
Messages: 5
Registered: July 2011
Junior Member
Try out some different values for the BIT_RATE keyword of the AddVideoStream() function. The default value is 2000000- meaning the encoder will aim to squeeze every second of video into 250 kilobytes (2Mbps = 250KBps), even if it has to sacrifice some quality to do so. H.264 is pretty good, but squeezing ~62 million pixels into 250KB is still a tall order.

Since you've gone through the trouble of getting yourself H.264 support (good choice!), you might also try experimenting with the PRESET keyword as well. Most of the H.264 presets just set different priorities for the tradeoff between video quality and encoding speed- if you don't mind encoding taking a bit longer, you can get a little more quality with the slower presets. The lossless presets will guarantee absolutely perfect quality, but fewer video players support them (Windows Media Player doesn't, but VLC does), and the files can come out quite large- here, the BIT_RATE setting is ignored, and slower presets get you smaller files rather than better quality.

I did an experiment a while back to see how the different presets compared. The quality column is completely subjective to my eyeballs. Your experience may vary, depending on your video. (My apologies for how ugly this table is going to be if you're not viewing with a monospaced font.)

Preset Time (s) Quality (/10) Size (KB)
ultrafast 9 4 3941
superfast 14 7 4306
veryfast 21 7 4532
faster 36 7.5 4487
normal 36 7.5 4488
fast 48 8 4553
default 54 8 4521
medium 54 8 4532
hq 89 8.5 4479
slow 91 8.5 4483
slower 157 9 4464
veryslow 307 9 4468
max 796 9.5 4454
placebo 893 9.5 4482
lossless_ultrafast 14 10 129048
lossless_fast 26 10 116800
lossless_medium 47 10 102583
lossless_slow 80 10 99142
lossless_slower 113 10 97086
lossless_max 460 10 96881


-Andrew Magill
ExelisVIS

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