Trim CAVS — Free Online Tool
Trim a CAVS (Chinese Audio Video Standard) file to a precise start and end point, keeping the original H.264 video and AAC audio streams intact via stream copy — no re-encoding, no quality loss. Ideal for quickly cutting segments from CAVS broadcast content without touching the compressed data.
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FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your CAVS file here
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Settings
Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
This tool uses FFmpeg's stream copy mode (-c copy) to trim your CAVS file by seeking to a specified start timestamp and cutting at a specified end timestamp, then writing the selected segment to a new CAVS container. Because both the input and output are CAVS files sharing the same H.264 video and AAC audio codecs, FFmpeg does not need to decode or re-encode any data — it simply copies the raw compressed bitstream packets that fall within the requested time range. This means the trim operation is extremely fast and introduces zero additional compression artifacts. The trade-off is that the cut points are constrained to keyframe (I-frame) boundaries in the H.264 stream, so the actual trim may be slightly imprecise at the start if no keyframe exists exactly at the requested timestamp.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary, the open-source multimedia processing engine that powers this tool via its WebAssembly (FFmpeg.wasm) build running entirely in your browser. |
-i input.cavs
|
Specifies the input CAVS file. FFmpeg reads the CAVS container, identifying the H.264 video stream and AAC audio stream inside it, in preparation for the trim operation. |
-ss 00:00:00
|
Sets the trim start point at zero (the very beginning of the file). Change this timestamp to any HH:MM:SS value or decimal seconds to begin the output clip at a different point in the CAVS file. |
-to 00:00:10
|
Sets the trim end point at 10 seconds into the CAVS file. Adjust this to any later timestamp to capture a longer or differently positioned segment from the source recording. |
-c copy
|
Instructs FFmpeg to copy both the H.264 video stream and the AAC audio stream directly from the CAVS input to the CAVS output without decoding or re-encoding, making the trim fast and lossless in terms of compression quality. |
output.cavs
|
The destination filename, written as a CAVS container. Because both input and output share the CAVS format with the same H.264 and AAC codecs, no format conversion takes place — only the selected time segment is written to this new file. |
Common Use Cases
- Extract a specific news segment or broadcast clip from a longer CAVS recording captured from Chinese digital television, without degrading the original broadcast quality.
- Trim a CAVS file down to the relevant scene before sharing it with a post-production team that requires CAVS format for compliance with Chinese broadcast standards.
- Remove a lengthy intro or outro from a CAVS-encoded presentation or training video to create a focused excerpt for distribution.
- Cut a short preview clip from a large CAVS broadcast archive file to use as a reference sample without re-encoding or changing the container format.
- Isolate a specific time-coded segment from a CAVS file for quality inspection or codec analysis while preserving the original H.264 and AAC bitstreams exactly.
- Quickly split a long CAVS recording session into shorter segments by running multiple trim operations with different start and end timestamps.
Frequently Asked Questions
No. Because the input and output are both CAVS files using the same H.264 video and AAC audio codecs, FFmpeg uses stream copy mode (-c copy), which copies the compressed bitstream directly without decoding or re-encoding. This means there is absolutely no additional quality degradation from the trim operation itself. The only quality already present is whatever lossy compression was applied when the original CAVS file was created.
When using -c copy (stream copy), FFmpeg cannot cut mid-frame — it must begin the output at the nearest H.264 keyframe (I-frame) at or before your requested start time. If your CAVS file has widely spaced keyframes, as is common in broadcast-encoded content, the actual start point may be a few seconds earlier than specified. To achieve frame-accurate trimming, you would need to re-encode the video, which this tool avoids to preserve quality.
Yes, in most cases. Since both video and audio are copied without re-encoding, their relative timing is maintained from the source CAVS file. However, because the video cut snaps to a keyframe boundary, FFmpeg adjusts the audio start accordingly to keep sync. The result should be a properly synchronized CAVS output as long as the source file had correct audio/video alignment.
Yes. The -ss flag sets the start time and -to sets the end time, both in HH:MM:SS format or in decimal seconds (e.g., -ss 30 -to 90 for a 60-second clip starting at the 30-second mark). You can also replace -to with -t followed by a duration instead of an end timestamp — for example, -t 00:01:00 to capture exactly 60 seconds from the start point. Adjust these values in the displayed command and run it locally with FFmpeg for files over 1GB.
The command as shown processes a single file, but you can adapt it for batch processing in a shell script on your local machine. On Linux or macOS, a simple for loop — for f in *.cavs; do ffmpeg -i "$f" -ss 00:00:00 -to 00:00:10 -c copy "trimmed_$f"; done — will apply the same trim to every CAVS file in a directory. On Windows, a similar approach works with a batch file using a for loop. This is especially useful for archives of broadcast recordings that need the same segment extracted from each file.
CAVS is a Chinese national standard format and is not as universally supported as MP4 or MKV. Playback depends on the player having a CAVS-compatible demuxer. VLC and FFmpeg-based players generally support CAVS containers, but many consumer devices and web browsers do not. If you need broader compatibility after trimming, consider using a separate conversion tool on this site to re-wrap or transcode the trimmed CAVS file into a more widely supported format such as MP4.
Technical Notes
CAVS files in practice typically carry H.264 video encoded with libx264 and AAC audio, which are both mature, well-supported codecs — meaning the trim operation via stream copy is highly reliable. The CRF-based quality scale (0–51, default 23) and AAC bitrate options (default 128k) are irrelevant during a stream copy trim since no encoding occurs, but they would matter if you ever needed to re-encode the CAVS output. CAVS does not support embedded subtitles, chapters, or multiple audio tracks, so there is no risk of losing any of those elements during trimming — the format simply does not carry them. One important limitation: the -c copy approach means the output file's duration metadata may occasionally be slightly off in certain CAVS muxers, as the container relies on the keyframe-aligned segment rather than the exact requested timestamps. If precise metadata accuracy is critical for broadcast compliance, verify the output duration with ffprobe after trimming.