AVC most often refers to H.264/AVC, which is the compression scheme, not the container that packages audio, video, and metadata, and everyday formats like MP4, MKV, MOV, and TS simply wrap an AVC video track plus audio, causing confusion when people call the whole file “AVC” even though the container defines it; an extension such as .avc or .h264/.264 usually indicates a raw bitstream or proprietary output that VLC might open but with limited navigation, inaccurate length, or no audio since containers normally provide timing data and allow multiple streams.

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 works as a full-featured MP4 *container*—with organized video, audio, indexes, timing data, and metadata—while a `.avc` file typically lacks these container elements and is simply a raw AVC stream or device-specific file; it can decode, but players may show misreported length since crucial structural information isn’t included.

This is also why `.avc` files frequently have silent playback: audio might be stored separately or never included at all, while MP4 commonly bundles both streams; plus, some CCTV/DVR systems mislabel their exports, so a file that’s really MP4 or TS could appear as `.avc` until renamed to `.mp4`, though certain devices use proprietary wrappers that require their own players; ultimately, `.mp4` tends to represent a well-formed container, whereas `.avc` often signals video without container info, which explains missing audio, poor seeking, and playback quirks.

Once you figure out what your “AVC file” actually is, the next move depends on whether it’s mislabeled, a raw H.264 stream, or a proprietary CCTV/DVR export; if MediaInfo or VLC reveals it’s in a normal container (e.g., showing “Format: MPEG-4” or behaving like a standard video), the easiest fix is usually renaming the extension—many devices save MP4s but call them `.avc`, and switching `clip.avc` to `clip.mp4` often makes it universally playable (always duplicate the file first); if it turns out to be a raw H.264 stream, usually identified by “Format: AVC” with minimal container details and odd seeking, the typical remedy is to remux it into MP4 without re-encoding so it gains proper indexing and timing for smooth 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 wrap successfully 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.