[Gamester17]

64MB RAM memory upgrade to 128MB RAM memory will not be of much benefit to XBMC during video playback (nor for music with visualization) as XBMC's MPlayer and DVDPlayer cores are not designed to take advantage of the extra the extra memory. (They are however designed to take advanta of a faster 1.4GHz CPU if available).

@senorphatnutz; .mp4 files usually contain MPEG-4 AVC (H.264) video and AAC (Advanced Audio Codec) audio, both of which require much more processing power to be decoded then MPEG-2 / MPEG-4 ASP (H.263) video and MP3 audio. So the CPU is the bottleneck for MP4 video files long before the memory becomes an issue.

Please read these hints and tips from the XBMC online manal for more information

http://www.xboxmediacenter.com/wiki/inde...imitations

* With its 733Mhz Intel Pentium III and 64MB shared memory, the Xbox game-console does not have enough hardware-resources (not fast enough CPU nor large enough RAM-memory) to play 720p/1080i resolution-native HDTV video (at 1280x720 and 1920x1080 pixels), (like 720p/1080i WMV HD or MPEG-2). Workaround: XBMC can however upconvert all 480p/576p standard-resolution movies and output them to 720p or 1080i HDTV resolutions in better quality than most (if not all) HDTV's native function to upconvert video.

* Again with its 733Mhz Intel Pentium III and 64MB shared memory, the Xbox does not have enough hardware-resources (not fast enough CPU nor large enough RAM-memory) to play MPEG-4 AVC (H.264) encododed videos with Cabac and Deblocking if the video-resolution is higher than 352x288 pixels. Workaround: If you encode your MPEG-4 AVC (H.264) videos without Cabac and Deblocking then the Xbox hardware can handle up to 480x576 pixels video-resolution. Though best is to encode your videos to MPEG-4 ASP (like DivX or XviD) instead, then the videos native-resolution can be up to 960x540 pixels (a.k.a. HRHD resolution).

http://www.xboxmediacenter.com/wiki/inde...an_I_do.3F

Q: I use XBMC in HDTV resolution (720p or 1080i) and when I try play a video or audio file/stream it fails, what can I do?
A: Most likely you are running out of available RAM (Random Access Memory). The Xbox hardware only comes equipped with 64MB of unified RAM, (which means that system and graphics memory are shared, unlike a standard PC where they are separate dedicated memory for both the system and the graphics, and usally both are much larger than 64MB by themself). 64MB of total RAM is not a lot, and is especially limiting at high-definition HDTV like 720p (1280x720) and 1080i (1920x1080) pixel-resolutions. This means that when you use 720p or 1080i you have to be mindful of things that can take up memory:

Cache sizes (especially video cache, this does normaly not have to be larger than 2MB, maybe 4MB or max 8MB or wireless)
Skin used (some skins use more memory than others, try to use XBMC default Project Mayhem 3 skin)
Enabled servers/services (WebServer, FTP-server, Python)
If you are having problems in 1080i then try if it works better in 720p (if your display supports 720p that is)
Try running video-playback at a lower resolution than the GUI, for example videos in 720p and GUI in 1080i
Due to the shortage of RAM, it may be a wise idea to turn off all of the listed servers/services at first until you know what can be sustained. Also lowering the video/audio/stream cache size to 1MB, (which is more than enough for playback over a wired local network). If you use wireless, then you may need it slightly higher, (though expect other problems with streaming video over wireless, see Wireless Specific Tips for more information).

http://www.xboxmediacenter.com/wiki/inde...V_media.3F

Q: Does XBMC and Xbox support HDTV (High Definition TV) resolutions?, and HDTV media?
A: Yes and no, but the answer is a little more complicated than that, you see: Xbox/XBMC can output a 480p/720p/1080i signal (if you have a Xbox High Definition AV Pack/component cable) and upscale all low-resolution videos (like retail DVD-Video/Movies) to 720p (1280x720 pixels progressive) or 1080i (1920x1080 pixels interlaced) in hardware (linear upscale/upconvert). So XBMC have no problems with upscaling for example DVD-Video (720x480 NTSC/720x756 PAL) movies to HDTV 480p/720p/1080i. XBMC is even capable of playing native HD video (video/movies with native resolutions higher than 720x576) like 720p (1280x720) and 1080i (1920x1080), however there is here a big snag/limitation with that and that is that a standard Xbox only has a 733Mhz Intel Pentium-III CPU (processor) and that does not have the processing power to decode those native HD videos fast enough, (Microsoft® and DivX® recommends a 2.4 Ghz PC + 384MB RAM for 720p MPEG-4 playback!). This means that you might only get maybe 10-20fps (frames per seconds) displayed which would appear so jerky because of all dropped frames that it will be un-viewable. The only real solution if you want to play videos with native HD resolutions on Xbox is to buy or upgrade to a non-standard Xbox with a much faster CPU (processor), (like example the DreamX-1400 from FriendTech] which has a 1480Mhz Pentium-III that is at least capable of decoding all native HD videos encodec with MPEG-2 or MPEG-4 ASP (H.263) that are have up to 720p in native HDTV video resolution. FriendTech do offers trade-in). Note! You must enable/setup your HDTV settings in Microsoft dashboard, (on NTSC Xboxes).

To make this even clearer XBMC capability on a standard Xbox (with Intel 733Mhz PIII CPU):
720x480 pixel video output to 480p HDTV (720x480 progressive) = OK! (eg not upscaled).
720x480 pixel video output to 720p HDTV (1280x720 progressive) = OK! (eg upscaled).
720x480 pixel video output to 1080i HDTV (1920x1080 interlaced) = OK! (eg upscaled).
1280x720 pixel progressive video output to 720p HDTV (native 1280x720 progressive) = FAIL!
1920x1080 interlaced video output to 1080i HDTV (native 1920x1080 interlaced) = FAIL!

Note! All above that state FAIL don't actually fail to play, it's just that the Xbox CPU is to slow to decode/render the high resolution so it will drop so may frames (producing stuttering playback) that is will be un-viewable.