Convert TMP to MP4

An interrupted recording, export, camera transfer, or download can leave a .tmp file when a player, editor, upload service, or device requires MP4. First determine whether the file already contains readable video, because many TMP files are not media files and cannot be converted.

What TMP files are

TMP is a generic temporary-file extension, not a defined video format. Applications, browsers, installers, cameras, screen recorders, and editing software use it for unfinished output, caches, recovery data, downloads, or internal workspace files.

A TMP file may contain a complete video under a temporary name, an incomplete MP4/MKV/TS stream, media fragments, project data, or unrelated binary data. The program that created the file is the best recovery option: reopen its project or recording session and use its recovery, save, export, or download-resume function before attempting conversion.

Do not rename, move, or delete a TMP file while its creating application is still running. Make a copy after closing the application, and perform tests only on that copy.

What MP4 files are

MP4 is an ISO Base Media File Format container for video, audio, subtitles, chapters, and metadata. It commonly contains H.264/AVC or H.265/HEVC video and AAC audio, and it is accepted by most phones, TVs, web services, media players, and editing applications.

MP4 compatibility depends on its internal streams, not only its extension. H.264 video with AAC audio is the safest choice for older devices and web upload services; H.265/HEVC can reduce file size at similar quality but is less compatible with older hardware and some editors.

Identify the TMP file before converting

1. Copy the file to a separate folder and retain the original.
2. Open the copy in VLC using Media → Open File. VLC can identify many media streams even when the filename extension is unknown, but it cannot reconstruct missing video data.
3. Inspect the file with MediaInfo, or run ffprobe input.tmp if FFmpeg is installed. Video and audio stream details indicate that the file is likely usable media.
4. If the inspection identifies a complete MP4 container, rename only the copy from recording.tmp to recording.mp4 and test it in VLC. Renaming changes the filename only; it does not convert, repair, or complete the file.

A browser's partially downloaded TMP file usually must be resumed or downloaded again through that browser or service. A video editor's cache, proxy, autosave, or project TMP file is not source footage and should be recovered through the editor rather than converted.

Remux readable media without quality loss

If VLC or FFprobe recognizes video and audio, FFmpeg can write a new MP4 container without recompressing the streams:

ffmpeg -i "input.tmp" -map 0 -c copy -movflags +faststart "output.mp4"

-c copy copies streams exactly, so it is fast and causes no generation loss. -movflags +faststart places MP4 indexing metadata near the start of the output, which helps progressive web playback. This command works only when FFmpeg can read the input and the contained streams are valid in MP4.

If FFmpeg reports an unsupported codec, invalid timestamps, or a stream that MP4 cannot contain, re-encode to a broadly compatible MP4:

ffmpeg -i "input.tmp" -c:v libx264 -crf 18 -preset medium -pix_fmt yuv420p -c:a aac -b:a 192k -movflags +faststart "output.mp4"

Lower CRF values produce higher quality and larger files. Use 18 for high quality or approximately 20 to 23 when a smaller file matters more than preserving fine detail.

Use desktop applications without commands

HandBrake can re-encode a TMP file that it successfully opens. Select the source, set Format to MP4, choose H.264 video and AAC audio, select an output ending in .mp4, and start the encode. HandBrake cannot process proprietary temporary data or repair a recording whose essential data was never written.

VLC can convert playable media through Media → Convert / Save → Add → Convert. Select an MP4 profile using H.264 video and AAC audio, set an .mp4 destination, and start conversion. Use FFmpeg stream copying instead when possible, because VLC conversion normally re-encodes the video.

Online conversion and recovery limits

CloudConvert and Convertio may accept a TMP file when their file inspection recognizes it as media. Upload only non-sensitive files: temporary recordings can contain private video, audio, location data, or embedded metadata. Online services cannot convert an application cache, proprietary recovery file, encrypted data, or an unfinished recording with no readable media streams.

Errors such as moov atom not found, Invalid data found when processing input, or no detected streams commonly mean that an MP4 recording was interrupted before its index was written, the file is incomplete, or it is not video. Recover through the creating application, resume the original download, locate an autosave or original recording, restore a backup, or use a repair service that supports the specific camera or recorder. A converter cannot recreate frames that were never saved.