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H264 compression…the same only different
I have a file that I have exported from FCP using two methods, the codec and settings are the same. The clip is 55 seconds long. The sequence is in Apple HDV.
First I export the file.
File–>Export–>Quicktime Movie–>Options H264, Current frame, size etc. The File took about 2:40 seconds to render and the result was a file that was 90.88MB and 13.5 mb/secThen I tried this method: I simply changed the sequence setting to H264. I used the sequence–>settings menue and changed the compressor to H264. That was the only change. I had to render the video in the timeline, but it only took about 1:20 seconds. Then I exported a Final Cut Pro Movie. The export was very fast and the result was a file that was only 33/6 Megabites and 5015 kbits/sec.
When I play these files I cant tell them apart. So why is the one file so much smaller? And, if its so much smaller why does it look just as good?
DWR
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4 Replies
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Hi David,
Very interesting observation and question.
You had “Key Frames” and “Data rate” in automatic?
rafael -
[David Rowan] “When I play these files I cant tell them apart. So why is the one file so much smaller? And, if its so much smaller why does it look just as good?”
The H.264 encoder has controls for quality and data rate. The two export methods you used influence those controls differently. Often, the goal in encoding is to get the smallest data rate that still achieves adequate visual quality. The smaller of your exports is going toward that ideal. The larger of the two files is obviously wasting bandwidth for no gain in visual quality. Perhaps you can go smaller still with good results.
I like to compress to delivery codecs in Compressor or Squeeze because I can get better control over all the idividual settings of the encoder.
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Another thing that account for the data rate is the audio. When you export from the FC time line just changing the codec, you are keeping PCM audio that takes some 1,5 Mbps.
As tom says, if both look the same, go to the smaller.
Anyway the thing is that there is not real control about the process. I’m exporting as well H264 with 500Kps and only one pass.
I’ve been trying three different ways;
– With Compressor.
– From FC with QT Conversion.
– From FC with Batch Export.
So far with the Batch export the process takes the half of the time than with the others.
Don’t no way having the same setting.
Cheers,
Rafael -
Ken Stone has an in depth article on exporting using H.264 codec. Just google Ken Stone h 264 to find it.
Thanks,
Mike
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