Free online DAV to ASF converter

What the DAV format is

DAV is a proprietary video container used by many CCTV and DVR/NVR systems, including equipment from Dahua and other surveillance manufacturers. Recorders typically create DAV files when saving camera footage to an internal disk, USB drive, or network share.

A DAV file may contain proprietary video codecs, timestamps, watermark data, multiple camera channels, or access restrictions. Standard media players and general-purpose converters often cannot decode it directly. The recorder's supplied playback or export software, commonly called Smart Player or a vendor-specific video player, is usually the most reliable way to open and export the footage.

What the ASF format is

ASF, or Advanced Systems Format, is a Microsoft container designed for streaming and storing synchronized audio and video. It commonly contains Windows Media Video encoded with wmv2 and Windows Media Audio encoded with wmav2.

ASF can be useful when a legacy Windows application, media server, or archival system specifically requires a Windows Media container. It supports timestamps, streaming-oriented metadata, and relatively low bitrates, but it is less widely supported than MP4 and may not preserve surveillance-specific features such as event indexes, camera overlays, or proprietary authentication data.

How to actually convert DAV to ASF

1. Export the DAV footage to a standard video file

Install and open the playback/export utility supplied with the DVR or camera system. Add the DAV file, select the required camera and time range, then use a menu path such as Open file → Export, Backup → Convert, or Save as AVI. Export to a standard format such as AVI, MP4, or another format that the utility supports.

If the recorder uses encryption or requires a proprietary password, only the manufacturer's software may be able to perform this export. Preserve the original DAV file because the export may omit recorder metadata, audio, multiple channels, or authentication information.

2. Encode the exported video as ASF with FFmpeg

Install FFmpeg, open a terminal in the export folder, and run:

ffmpeg -i exported.mp4 -c:v wmv2 -b:v 2M -c:a wmav2 -b:a 128k converted.asf

Replace exported.mp4 with the actual exported filename. The command re-encodes video as Windows Media Video and audio as Windows Media Audio, improving compatibility with ASF-oriented software. Adjust -b:v 2M to match the source resolution and required file size; higher bitrate generally retains more detail but produces a larger file.

For footage without audio, use:

ffmpeg -i exported.mp4 -c:v wmv2 -b:v 2M -an converted.asf

Test whether FFmpeg can read the DAV directly with ffmpeg -i recording.dav. If FFmpeg reports an unknown format, invalid data, or missing codec, use the manufacturer's export utility first rather than renaming the extension.

You can also convert the file on 101convert.com for free without installing software, provided the service accepts that particular DAV file and can decode its proprietary stream. A vendor export is still preferable for protected or sensitive surveillance footage.

Quality, compatibility, and limitations

Conversion from DAV to ASF normally involves at least one decode and re-encode operation, so the ASF file may lose detail, especially in dark scenes or moving objects. Match the output frame rate and frame size to the exported source when necessary; FFmpeg can preserve common values automatically, but incompatible source parameters may be converted.

ASF does not guarantee preservation of DVR-specific data. Verify the converted file's timestamp, audio, camera number, overlays, and playback duration before deleting the original. ASF support is limited in many modern editing applications, so use MP4 instead when ASF is not a strict compatibility requirement.