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Any ideas about a good 1080p to 720p converter that is able to convert a video of 90 minutes in less than several hours? (maybe like in 2, 3 or 4 hours ;-)
The compression of a file is H.264/MPEG-4 AVC.

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3 Answers

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If you want to stay with H.264, you'll probably want to go with x264 as encoder. It's built into many applications, but most prominently FFmpeg with the "libx264" codec, or Handbrake.

x264 has a reputation of being fast and efficient. The speed can be tuned by presets that are called, for example, "fast". They range from "ultrafast" to "veryslow". You can check x264's help by calling x264 --fullhelp, which will explain all the options for the presets.

Here are the flags for "ultrafast". They disable some advanced encoding functions that require processing time. Encoding in "ultrafast" mode will not be as efficient in terms of bits used, and with a fixed bit rate, you'll lose some quality. But generally, it shouldn't matter as much.

--no-8x8dct --aq-mode 0 --b-adapt 0
--bframes 0 --no-cabac --no-deblock
--no-mbtree --me dia --no-mixed-refs
--partitions none --rc-lookahead 0 --ref 1
--scenecut 0 --subme 0 --trellis 0
--no-weightb --weightp 0

Handbrake

You can for example enter them in Handbrake's option string when looking under "Advanced":

enter image description here

Just copy this string, found here:

ref=1:bframes=0:cabac=0:8x8dct=0:weightp=0:me=dia:subq=0:rc-lookahead=0:analyse=none:trellis=0:aq-mode=0:no-deblock=1:scenecut=0:mbtree=0

Don't forget to rescale by going to the Picture Settings.

FFmpeg

Or, use them in FFmpeg by simply calling the right preset:

ffmpeg -i input.mp4 -vcodec libx264 -preset ultrafast -s 1280x720 -acodec copy output.mp4
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Is it gonna take longer if the source file is on a DVD comparing to having it on my hard disk? – Einsteins Grandson Jan 22 '12 at 2:08
Yes, most probably. However, if you already have the DVD ripped to h.264, note that re-encoding from an already encoded file might result in noticeable quality loss. You'd have to set the RF (rate factor) accordingly (e.g. lower = better) to compensate. In this case, ripping from DVD again will probably leave you with better quality. It's always a tradeoff between speed and quality. – slhck♦ Jan 22 '12 at 2:11
I don't have a problem with loosing the quality and it's not a normal DVD... It was a 1080p file that was burned on a DVD... – Einsteins Grandson Jan 22 '12 at 2:15
I see. In this case, hard disk read speeds are of course faster. – slhck♦ Jan 22 '12 at 2:17
@user1111261 Did it work for you? – slhck♦ Jan 23 '12 at 22:05
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up vote 0 down vote

If you are looking for something like real-time speeds or better, you could look into using your GPU for encoding.

Here's an article titled "H.264 encoding - CPU vs GPU: Nvidia CUDA, AMD Stream, Intel MediaSDK and x264" that you might be interested in reading.

The quality you'll get from a GPU based encoder is nowhere near what x264 can deliver (sometimes destroying frames completely). However, if you're using the fastest settings you can configure for x264, it might be worth comparing those results.

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up vote 1 down vote

I use Handbrake for all my conversions. But I can't tell how fast will it be for you.

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Depends on the hardware, of course. But you can tune Handbrake with its advanced options – see my answer. – slhck♦ Jan 22 '12 at 2:07

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