AVC typically means H. To check out more regarding AVC file online viewer visit the web site. 264/AVC compression, which is how video is encoded, not how it’s packaged, and most real-world videos live inside MP4, MKV, MOV, or TS containers that can hold AVC video plus audio streams, leading people to call an MP4 “an AVC file” even though MP4 is the real file format; when a file literally ends in .avc or .h264/.264, it often represents a raw stream or special-device export that might open in VLC but may have poor seeking, bad duration data, or missing audio because only containers provide indexing and multi-track structure.

Some CCTV/DVR systems generate videos with strange extensions though the video may still be standard, allowing a rename to .mp4 to work, while others need the manufacturer’s software to re-export; to identify the type quickly, open in VLC, check codec info, or run MediaInfo to see if it’s a normal container with audio, and if it shows as a raw AVC stream you typically remux it into an MP4 container to improve seeking and compatibility without recompression.

A `.mp4` file is almost always a true MP4 *container* holding compressed video plus audio, subtitle tracks, metadata, and seek/timing structure, whereas a `.avc` file is often merely a raw H.264/AVC stream or vendor-specific output; although playable, it commonly leads to strange initial playback because container elements aren’t present.

This is also why `.avc` clips often carry no audio at all: audio is frequently separate or never included, unlike MP4 which typically bundles both streams; meanwhile, some CCTV/DVR tools generate files with odd extensions, so a `.avc` may merely be a mislabeled MP4/TS that works after renaming, though proprietary ones require the vendor utility to convert; in summary, `.mp4` usually implies properly packaged media, while `.avc` often indicates raw video, causing playback inconsistencies and weak seeking.

Once you’ve determined whether the “AVC file” is mislabeled, raw H.264, or proprietary, you can pick the right fix; when VLC/MediaInfo shows a standard container—look for “Format: MPEG-4” or normal seek behavior—just renaming the `.avc` to `.mp4` often restores compatibility (after copying it), but if the file is a raw H.264 stream indicated by “Format: AVC” with sparse container details and erratic seeking, then the usual remedy is to repackage it into an MP4 container without re-encoding, adding essential timing and indexing data for proper playback.

If the clip was generated by a CCTV/DVR or similar device with a custom wrapper, the best solution is to use the official viewer/export tool to produce an MP4 or AVI, since some proprietary formats refuse to convert as-is until they’re exported properly; here you’re converting from a unique structure to a standard container, not just renaming, and if playback breaks, won’t load, or the timing is still wrong after remuxing, it likely points to corruption or absent companion files, making a new export or locating the index/metadata files necessary.