Saturday, 19 March 2011

AVI and MP4

Besides GVI and Flash Video, Google provided its content through downloadable Audio Video Interleave (.avi) and MPEG-4 (.mp4) video files. Not all formats are available through the website's interface, however, depending on the user's operating system.

Where available, Google's "save as" function for Windows/Mac produced an .avi file, while the "save as" function for iPod and PSP produced an .mp4 file.

This .avi file was not in standard AVI format. To play the file in a popular media player such as Winamp or Windows Media Player, the file had to first be modified, using a hex editor to delete the first LIST block in the file header, which started at byte 12 (000C hex, first byte in file is byte 0) and ended at byte 63 (003F hex).[10][11] Optionally, the file length (in bytes 4 to 7, little endian) should also be amended, by subtracting 52 (3F hex - 0C hex = 33 hex).

Winamp and Windows Media Player cannot play the unmodified .avi file because the non-standard file header corrupts the file. However, Media Player Classic, MPlayer, the VLC Media Player and GOM Player will play the unmodified .avi file, and the Google .mp4 file. Media Player Classic can do so only if an MPEG-4 DirectShow Filter, such as ffdshow, is installed. Most Linux media players (including xine, Totem, the Linux version of VLC Media Player, and Kaffeine) have no problem playing Google's .avi format.

An .mp4 video file will play in Winamp 5 if an MPEG-4/H.264 DirectShow Filter such as ffdshow and an MP4 Splitter such as Haali are installed, and the extension ;MP4 is added to the Extension List in the Winamp DirectShow decoder configuration.

In the Spring of 2008, the option to download files in .AVI format was removed. Files were henceforth only available as Flash video or .MP4 video. The same videos, when accessed through the companion site, were available only in Flash video format.

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