Under the Hood: File Analysis Tools for Streaming Video
Information about the hinted tracks proved particularly useful when producing with Telestream Episode, since the program allocates a disproportionately high data rate to the Hinted video track—approximately 3–4 times higher than other encoders. For example, in Quicktime Player's Movie Properties window, you can see that the data rate for the hinted video track is higher than the actual streamed video. While this shouldn’t affect actual streaming bandwidth, since the hinted track never leaves the server, it does make the file look disproportionately large from a file-size standpoint, which is disconcerting. QuickTime’s Movie Properties window is the only tool that explains why the Telestream file is much larger than files produced by other encoding tools.
Other than this unique capability, however, QuickTime Player falls well short of other MOV analysis tools on the Windows and Mac platforms. Probably the best alternative is MediaInfo, which is similarly available on both platforms.
GSpot
GSpot is a free, Windows-only file tool you can download from http://gspot.headbands.com. To get up and running, you download a zipped file containing the Gpot.exe file, which never really installs itself. Instead, you just click the EXE file when you want to analyze a file, which runs the program. I prefer not to install shareware programs, and I like this mode of operation. Once up and running, you can load files via a File > Open menu command, or via drag and drop.
GSpot was originally designed as kind of a geeky diagnostic tool to help identify the codecs necessary to view a particular file. As such, it’s got some compelling features, such as the ability to display all codecs and filters on your computer and track the video and audio rendering chain that displays your media. The program also offers some great functionality for MPEG program or elementary streams, where it can show groups of pictures color coded by frame type, with overlays for B-frame redundancies and actual frame numbers in the GOP. Definitely fun stuff.
However, most of the Video section, including these details, remains grayed out for Windows Media files, as well as MOV and FLV files, indicating a drop in utility for streaming file analysis. There are some bright spots, such as revealing the date of file creation as well as any metadata packed with most files. You can see the latter in the GPot interface, where Sorenson Squeeze 5.0 sneaks in a mention as the encoding tool. GSpot also calculates the frame quality (Qf), or bits/pixel-frame. This is a nice way to compare the per-pixel data rate of files with disparate frame sizes or frame rates.
For all streaming formats, you get the basics, with video data rate and frame rate calculated rather than simply reported from the file header or metadata. Strangely, the program failed to display a frame rate for all Windows Media files that I tested, though it worked for other streaming formats.
When analyzing Windows Media files, GSpot fails to reveal any details of the multiple streams, or the WMFSDK version used to produce the file. Similarly, with Flash, GSpot provides basics that may not be available in your Flash Player, such as codec and calculated frame rate and data rate, but no information you can’t get from MediaInfo.
With H.264 files, GSpot again falls behind MediaInfo, failing to provide profile and level, or whether the file was produced with CABAC or CAVLC encoding. GSpot also doesn’t show the audio data rate for all AVC-encoded files, which MediaInfo always provided.
You can configure GSpot to write out reports containing all reported data for each file analyzed, a simple way to track and accumulate file-based data. You can create separate reports for each file or accumulate all reports in a single file, and analyze a folder full of files in batch, another nice convenience. Overall, GSpot is competent, but its primary strengths lie outside the streaming market, and it’s best-suited for MPEG-2 and AVI file analysis.
Inlet Semaphore
Inlet Semaphore ($995) is the only true quality control tool of the bunch, and reviewing it in situ only heightened my appreciation for its capabilities. That said, it also revealed a number of issues—some minor, some more serious—that hopefully Inlet can address in a subsequent release. Make no mistake, however—if automated multicodec quality control is your goal, the Windows-only Semaphore is the only product that fits the bill. Don't worry; you don't need to spend $995 to test out Semaphore, as there's a free trial available. Check it out.