AVC generally means H.264/AVC video compression, which is the encoding layer, not the wrapper, while the actual file format is usually a container like MP4, MKV, MOV, or TS that can hold AVC video along with audio tracks such as AAC, so people sometimes mix things up and label an MP4 as “an AVC file” despite the container defining the type; files ending in .avc or .h264/.264 usually contain raw AVC streams or custom exports that VLC may handle but often with weak seeking, incorrect duration, or no audio due to missing container-level indexing.
Some CCTV/DVR units assign quirky extensions to recordings despite the content being standard, so renaming to .mp4 often works unless the file is genuinely proprietary and must be processed in the vendor’s export tool; the fastest approach is testing in VLC, checking codec details, or using MediaInfo to see if it’s a proper container format with audio, and if it’s actually a raw AVC stream you’ll usually need to wrap into an MP4 container for smoother playback and navigation.
A `.mp4` file generally provides a complete MP4 *container* with video, audio, subtitles, metadata, and timing/index data that ensures smooth playback, while a `.avc` file often signals a raw AVC bitstream lacking container features; it may still display video, but players can struggle with jumping in the timeline due to missing structural cues.
This is also why `.avc` files frequently have no built-in sound: 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 a custom vendor format, which explains missing audio, poor seeking, and playback quirks.
Once you confirm what your “AVC file” actually represents—misnamed MP4, raw H.264, or proprietary—the next action is straightforward; if MediaInfo or VLC identifies it as a regular container like MP4 (showing “Format: MPEG-4” or smooth seeking), renaming `clip.avc` to `clip.mp4` usually works, provided you make a backup; if instead the file is raw AVC (often shown as “Format: AVC” with minimal metadata and clumsy navigation), you should remux it into an MP4 container without re-encoding to add the indexing and timing structure missing from raw streams.
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.
