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Feature: Page (1) of 2 - 10/16/07

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Getting the best from YouTube

Which format is best for FLV conversion?

By Mike Jones

There is much to like about YouTube.  Its massive potential audience and simple functionality make it a very empowering platform for self broadcasting. But YouTube also has built-in shortcomings that can have serious impact on the quality of experience you can generate.

YouTube, like much of the video content on the web, uses the Flash Video (FLV) format and the On2 codec for end delivery. With little doubt the On2 codec delivers the best quality-to-size compression of any codec available for very low-bandwidth delivery. Not even AVC/h.264 can equal On2's sharp and smooth clarity at extremely low bitrates taking nearly twice the bitrate to look as good. YouTube defaults 320x240 frames at about 200kbps and these image specs are certainly capable of delivering a respectable on-line image in the FLV format.

What has been a problem is YouTube's insistent re-encoding to FLV. YouTube traditionally does not allow for uploading of video in FLV and this is compounded by the 100MB upload limit cap. Instead of a simple FLV, 20MB to 30MB upload for a 10 minute video; the user is forced to upload a lossy compressed video close 100MB in order to have some remnant of their original quality survive the re-compression process.

Now, however it seems this problem has been recently rectified by YouTube. While the YouTube Help pages declare the upload compliant formats as MPEG, AVI, MOV and WMV and even clearly state that ?YouTube does not currently accept videos in Flash (.flv) format? we have found that you can in fact upload FLV format video which is then mounted on YouTube natively without re-compression. While it was certainly strange (and problematic) that YouTube did not allow for FLV upload in the past, it seems even stranger that when it did implement this feature it remains un-declared on the site.

YouTube converts your videos to FLV.

YouTube's upload guide states its preferred format for upload is DivX (which is itself a variant of MPEG-4) at 320x240 resolution. Not only does this make no mention of FLV upload possibility which avoids any re-compression that a format such as DivX would suffer as it is transcoded to FLV for delivery, but this part of the site also presents a rather strange recommendation. YouTube advises that video in hi-bitrate WMV format in resolutions higher than 320x240 should be converted to MPEG-4 and then re-sized down to 320x240.... What would prompt YouTube to recommend a double layer of heavy lossy compression (which MPEG-4 is) on an already data-starved image (such as WMV) is quite beyond me. The site suggests that this convoluted process will ?help reduce the number of artifacts you end up with? but there is little logic or technical sense to the recommendation and in fact quite the opposite is true.

WMV is a lossy format usually running at less than 3mbps, depending on the source and what application or device made it. Unless you encode to an extremely high bitrate MPEG-4 (15-20mbps) the MPEG-4 is likewise a lossy compression. Then when the video goes to the YouTube servers it is re-compressed once more to Flash Video using the massively lossy On2 codec at just 200kbps. So why YouTube's own Help site would recommend a double lossy re-compression process seems to defy logic. . .

The other issue with YouTube's processing and delivery is related to frame size. Recommended specs are 320x240 and when YouTube re-compresses it does so to this sizing. But in displaying the media on the YouTube page, the video dimensions are inflated to 425x318. Subsequently the image, not displayed in its native resolution, appears overtly soft and unsharp with inevitable compression artifacts significantly exaggerated from their already under-nourished state.

And then there is the aspect ratio issue. Let?s be honest. 4:3 is dead. Widescreen is where it's at. DV Widescreen, AVCHD, HDV are all native 16:9 and even many mobile phone cameras are going widescreen; that's not to mention that its now nearly impossible to even buy a 4:3 TV or computer monitor or laptop - all have widescreen as standard. So why o' why does YouTube not allow for widescreen video other than letterbox (which effectively just throws away 1/3 of your valuable screen real estate)? The simple step to offering 400x225 as the widescreen equivalent of 320x240 would be a huge step forward.

For some time the FLV format has suffered a bad rap as people looked to YouTube for examples of FLV encoding and scoffed at the overt compression artifacts. But the truth is that FLV/On2 delivers absolutely outstanding compressed quality eclipsing h.264 at ultra low bitrates especially on fine graphics such as text. Instead, it is YouTube's processing that is the perpetrator of bad visual quality, not the format and codec of delivery.

One need only cruise the plethora of on-line video hosting sites to see virtually all the issues of YouTube's process dispensed with. BlipTV for example allows for FLV upload as well as virtually any other major format. Moreover, BlipTV allows for multiple video formats to be available to the user at their choice, including the original upload format. Brightcove is another example, providing FLV upload and even a locally hosted free FLV conversion tool where the creator can set the bitrate. These are but two examples amid a plethora of others (Revver, Metacafe, etc) that don't have the same restrictive encoding process of YouTube.