brohandy: AVI is only container. It is kind of envelope, that contains audio, video and subtitle streams. These streams can me encoded by different encoders to different stream formats. Audio stream could be raw PCM, MP3, MP2, AC3, DTS, AAC, etc., video stream could be MPEG4 (XVID/DIVX/....), AVC/H264, MPEG2, VC6, etc.. For every video file player needs to have some container splitter, which will extract audio/video/subtitle streams from the container, and decoders for encoded streams. In case there is some decoder missing or splitter is missing or cannot extract given stream format from container correctly, the file cannot be played. In the case above, AVI splitter cannot extract AVC/H264 stream to format, that H264 decoder understands. It is caused by incompatibility between AVI and H264 (standard H264 cannot be inserted to standard AVI).

As like Michal explained in http://www.mediamonkey.com/forum/viewtopic.php?p=342175#p342175 it could be non standard containers in AVI that some apps ignore but MM fail to play. More details would be needed.

Why is it that some videos, though all avi file types, won't display and some will? Are some projects missing a file or something important?

We will try to fix this for 4.1 version.

Unfortunately, my car video recorder stores video in this format.

Tracked as http://www.ventismedia.com/mantis/view.php?id=9484
But note, H264 in AVI is not standard, you should use e.g. MP4 or MKV for storing AVC/H264 stream.

VLC-player plays the video correctly. MM - only sound.

mediainfo:
[code]General
Complete name : C:\Users\Администратор\Desktop\123456.avi
Format : AVI
Format/Info : Audio Video Interleave
File size : 237 MiB
Duration : 4mn 0s
Overall bit rate mode : Variable
Overall bit rate : 8 259 Kbps

Video
ID : 0
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Main@L4.0
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Format settings, GOP : M=1, N=8
Codec ID : H264
Duration : 4mn 0s
Bit rate mode : Variable
Bit rate : 8 098 Kbps
Maximum bit rate : 8 001 Kbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate : 29.970 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.130
Stream size : 232 MiB (98%)

Audio
ID : 1
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : FF
Source duration : 4mn 0s
Bit rate : 128 Kbps
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 KHz
Compression mode : Lossy
Stream size : 3.67 MiB (2%)
Alignment : Split accross interleaves
Interleave, duration : 21 ms (0.64 video frame)
[/code]
debugview:[code]00000001 0.00000000 [952] Format plug-in constructor finished.
00000002 0.00713769 [952] TGenThread.Create: ThreadName: PlayThreadProc , Running Threads: Internal: 1, All: 33
00000003 0.01080820 [952] Thread 'PlayThreadProc' has started 6020
00000004 0.01086809 [952] Thread initialized 6020
00000005 0.01094928 [952] Player: Playback started
00000006 0.01122978 [952] Going 'PlaybackStarter_Var'to make final callback 3928
00000007 0.01131064 [952] PrepareDockedVideo: Begin
00000008 0.01136488 [952] PrepareDockedVideo: Reduced window or audio
00000009 0.03908346 [4488] f_video: SetVideoWindow, last:151004, new:161004
00000010 0.03925549 [4488] f_video: SetVideoPosition(32, 0, 515, 272)
00000011 0.08982495 [952] ControlsPlus.IsReallyVisible(): MainTree
00000012 0.08989849 [952] ControlsPlus.IsReallyVisible(): TBXTreeDock
00000013 0.09003059 [952] ControlsPlus.IsReallyVisible(): FMainWindow
00000014 0.09015603 [4488] f_video: Setting vertex pos: -0.883212, 0.879562, 1.000000, -1.000000
00000015 0.19574806 [4488] f_video: Cannot get IAMStreamSelect on splitter, trying VobSub
00000016 0.19586952 [4488] f_video: GetSubtitlesLanguages returns 8 bytes, sellang=-1, langcount=0
00000017 0.37756744 [4488] f_video: MediaMonkeyVHelper: message GetSubtitSett received
00000018 0.37768823 [4488] f_video: MediaMonkeyVHelper: message SetSubtitLang received
00000019 0.37779340 [4488] f_video: MediaMonkeyVHelper: GetAudioStreams failed, hr = 0x80004001
00000020 17.25777626 [952] TGenThread.Create: ThreadName: UpdateDriveLetters_Var , Running Threads: Internal: 1, All: 33[/code]