So I have a flash video that I tried converting to MPEG4 (H.264) in Adobe Premiere. I simply copied the .flv clip and the created a new sequence by dragging the clip to the new item icon:

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I this gave me a new Sequence with Sequence settings that matched the clip: enter image description here

I then go to Export where I want to maintain the aspect ratio of the clip, no black bars on the top, right, bottom or left. If I check "Match Sequence Settings" I cannot change the format, no surprises there:

enter image description here:

So I tried to do a custom H.264 and I unlink the Frame Width and Height, and a Pixel Aspect Ratio of square pixels but this gives me black bars on top and bottom (letterboxing) of the final Export, no surprises there:

enter image description here

Since I am amateur hour, I tried a free online flash to mpeg4 converter


This actually gave me the full screen mpeg4 with no letterboxing and you can see it in action here in Chrome, Firefox and Safari here (Press play button towards bottom center):


The thing is, I think the free online converter tool gave me some kind of messed up video because Chrome browser is making 3 requests for this video to download while it only makes one request for my Adobe Premiere video converted mpeg4 which you can see here:


So the mpeg4 converted using the online converter seems to be causing bugs in Chrome HTML video player over time so I want to try and figure out how to covert my flash to mpeg4, maintaining the aspect ratio, full screen video with no letterboxing.

Like you see here: http://beta2.cmykpress.com/

My Adobe Premiere export results so far are what you see here: http://beta2.cmykpress.com/Home/DifferentMpeg4

1 Answer 1


FLV is an Adobe container for streaming video. Historically, FLVs usually contained a variety of codecs (such as FLV1, Sorenson..etc) but nowadays it's usually H.264. Which is to say, the video may already be MP4 compatible. You may not need to recompress the video at all, and could simply transfer it from a FLV container to MP4, bypassing Premiere. ffmpeg is a tool that can do this. Download the 32-bit static build from here and the run the following command:

ffmpeg -i input.flv -c copy -movflags +faststart output.mp4

If the source video is not in fact H264, then try

ffmpeg -i input.flv -c:v libx264 -crf 23 -c:a aac -strict -2 -b:a 128 -movflags +faststart output.mp4

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