Under the Hood: File Analysis Tools for Streaming Video
When viewing WMV files in Media Player, the Properties window (File > Properties) identifies the total bitrate, resolution, audio and video codecs, and audio bitrate, and you can get the playback frame rate in the Statistics screen by clicking View > Statistics during the video playback. In addition to this data, I need to know which SDK I’ve used during encoding, since SDK 11 delivers slightly better quality, even with the older WMV9 codec.
When analyzing multiple bitrate files, I need to know the resolution, frame rate, and data rate parameters for each audio and video stream. If you’re a "tweaker," whether via the Windows Media Power Toy, command-line encoding, or a tool that incorporates the SDK 11 tweaks, you’d also like as many of these tweaks as possible exposed in the file analysis, but don’t hold your breath, since none of the tools provide this information.
MPEG-4 is a very complex algorithm with lots of configurable parameters. The free QuickTime Player provides some of the basics, including audio and video codecs, resolution, data rate (in kilobytes/second) and frame rate. This information is available in the free QuickTime Player, with some critical information about hinted files available only in QuickTime Pro.
Beyond this information, I’d love to know which H.264 codec was used to produce the file, since quality varies widely among them. I found no joy here, as no program identified the codec brand.
You’ll have better luck identifying the codec (MPEG-4 versus AVC) and profile used to produce the file, which most programs reveal. If you experiment with lots of encoding parameters, you’d probably like to know the B-frame interval and whether CABAC or CAVLC was utilized, since both affect the horsepower required to play the file.
When producing for a QuickTime server, you need to know if the file was hinted (i.e., whether control-data tracks were added), which QuickTime Pro can show you, and whether it was flattened (i.e., made accessible to multiple platforms) with a fast start header at the front of the movie. I found no tool that provided this last bit of data; the only piece of useful advice I found was to view the file header in a hex editor. If there’s an "mdat" string near the front of the file, it’s probably not a fast start; if there’s a "moov" string followed by an "mdat" string, it’s probably fast start.
I also found a free tool called Lillipot that will add fast start headers to a batch of MOV, MP4, M4V, and M4A files, which you can find at www.qtbridge.com/lillipot/lillipot.html.
Now that we know what to look for, let’s have a look at the five tools I considered.
QuickTime Player can open multiple instances on Mac and Windows, which makes it an essential playback tool for all QuickTime and H.264 producers. As a diagnostic tool, QuickTime Player is very limited, though if you upgrade to QuickTime Pro ($29.99), you can access unique data relating to hinted streaming files.
QuickTime Pro has two diagnostic screens, Movie Inspector (Window > Show Movie Inspector) and Movie Properties (Window > Show Movie Properties). Movie Properties provides the best view of hinted streaming files that I’ve seen, identifying the streams and showing their respective data rates. Note that data rate is not one of the default columns; you have to right-click the window and choose it and other desired columns from the context menu.
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