Free online AVC to H263 converter

What the AVC format is

AVC, also called H.264 or MPEG-4 Part 10, is a video compression standard used by smartphones, cameras, screen-recording software, streaming systems, and editing applications. AVC video commonly appears inside MP4, MOV, MKV, and 3GP files; a file with the .avc extension is often a raw H.264 elementary stream without audio or container metadata. FFmpeg, cameras, security systems, and professional video applications can create AVC streams.

What the H.263 format is

H.263 is an older video codec designed for low-bitrate videoconferencing and early mobile or multimedia hardware. It uses less processing power than many newer codecs and remains useful for equipment that specifically lists H.263 compatibility. Typical H.263 dimensions include QCIF 176×144 and CIF 352×288. H.263 is a codec rather than a complete media container, so an .h263 file normally contains video only.

How to convert AVC to H.263

FFmpeg is the most controllable desktop option. Install a current FFmpeg build, open a terminal in the directory containing the source, and run:

ffmpeg -i input.avc -c:v h263 -b:v 256k -r 15 -f h263 output.h263

Replace input.avc and output.h263 with the actual filenames. The command decodes AVC, encodes H.263 at 256 kbit/s and 15 frames per second, and writes a raw H.263 stream. For a raw AVC file that FFmpeg cannot identify automatically, specify the input demuxer:

ffmpeg -f h264 -i input.avc -c:v h263 -b:v 256k -r 15 -f h263 output.h263

For older hardware, match its documented frame size and bitrate, for example:

ffmpeg -i input.avc -vf "scale=176:144" -c:v h263 -b:v 128k -r 10 -f h263 output_qcif.h263

If the target expects H.263 inside a container rather than a raw stream, use the required container and extension instead. For example, a 3GP output can be created with:

ffmpeg -i input.avc -vf "scale=176:144" -c:v h263 -b:v 128k -r 10 -an -f 3gp output.3gp

The -an option removes audio because raw H.263 output cannot carry it; retain or encode audio separately when the target container supports an appropriate audio codec. You can also convert the file on 101convert.com for free without installing software.

Quality and compatibility limitations

This is a lossy transcode: AVC is decoded and then compressed again, so increasing the H.263 bitrate cannot restore detail already lost in the source. H.263 supports fewer features and lower practical quality than AVC, and some decoders accept only specific frame sizes, frame rates, pixel formats, or bitrates. Check the receiving device’s specification before choosing dimensions and bitrate. Use ffprobe input.avc to inspect the source resolution, frame rate, and stream type before conversion.