Convert HEVC to DSS — Free Online Tool
Convert HEVC video files to DSS audio format, extracting and transcoding the audio stream to ADPCM IMA OKI — the codec used by Olympus, Philips, and Grundig digital dictation devices. This is a specialized conversion that discards the H.265 video entirely and outputs a speech-optimized mono audio file compatible with professional dictation workflows.
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FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
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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
DSS (Digital Speech Standard) is a proprietary audio-only container designed specifically for dictation devices, and it supports only one codec: ADPCM IMA OKI, a low-bitrate adaptive delta pulse-code modulation variant tuned for human speech frequencies. During this conversion, FFmpeg completely discards the H.265 video stream from the HEVC file — no video re-encoding occurs. The audio stream (if present in the source file) is decoded from whatever codec it uses and then re-encoded into ADPCM IMA OKI at the low sample rate and narrow frequency range the DSS format expects. The result is a compact, speech-optimized audio file with no video data whatsoever. Because DSS targets dictation rather than music or general audio, expect significant fidelity reduction compared to the source — this format is engineered for voice intelligibility, not audio quality.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, which handles the reading of the HEVC container, decoding of its audio stream, and re-encoding into the DSS output format. |
-i input.hevc
|
Specifies the input file — an HEVC container holding an H.265 video stream and (typically) an audio stream. FFmpeg will parse both streams but only the audio will be used in this conversion. |
-c:a adpcm_ima_oki
|
Instructs FFmpeg to encode the audio stream using the ADPCM IMA OKI codec — the only audio codec supported by the DSS format, developed for low-bitrate speech storage on Olympus, Philips, and Grundig dictation hardware. |
output.dss
|
Defines the output file with the .dss extension, which tells FFmpeg to wrap the ADPCM IMA OKI audio in the Digital Speech Standard container. No video stream is written because the DSS format is audio-only. |
Common Use Cases
- Extracting dictated voice memos or verbal notes recorded as HEVC video on a smartphone and converting them to DSS for import into professional transcription software like Philips SpeechExec or Olympus Dictation Management System.
- Preparing voice-over reference recordings captured on a mirrorless camera (which outputs HEVC) for playback on a hardware digital dictation device that only accepts DSS files.
- Converting HEVC-encoded interview footage to DSS so a legal or medical transcriptionist can load the audio into their foot-pedal-controlled dictation player without needing video playback software.
- Archiving verbal field notes recorded as HEVC video on a modern action camera into a compact DSS format for integration with older dictation management systems that predate modern video support.
- Stripping video from HEVC recordings of spoken instructions or training narrations to create DSS files for distribution to transcription teams using Grundig-compatible dictation hardware.
- Testing DSS playback compatibility on dictation hardware using audio originally recorded in a high-efficiency HEVC container before committing to a larger batch workflow.
Frequently Asked Questions
Yes, and significantly so. DSS using the ADPCM IMA OKI codec is engineered exclusively for speech intelligibility at very low bitrates — it targets narrow frequency ranges suited to human voice, not full-spectrum audio. Any music, ambient sound, or high-frequency audio content in your HEVC file will be heavily degraded or lost entirely. For voice recordings, the spoken word will remain understandable, but this is a lossy, speech-specialized format and should not be used when audio fidelity matters.
The entire H.265 video stream is dropped. FFmpeg reads the HEVC container, ignores all video data, and only processes the audio track for re-encoding into ADPCM IMA OKI. The output DSS file is audio-only — the DSS format has no provision for storing video whatsoever, so no video data can be preserved regardless of source quality, resolution, or HDR metadata.
If the source HEVC file contains no audio stream, FFmpeg will produce an empty or invalid DSS file and likely report an error such as 'Output file does not contain any stream.' DSS is an audio-only format, so a successful conversion requires at least one audio track in the input. This situation can occur with HEVC files that contain only raw video streams with no accompanying audio.
DSS files created with ADPCM IMA OKI are intended for the Digital Speech Standard ecosystem developed by Olympus, Philips, and Grundig. Compatibility software includes Philips SpeechExec, Olympus Dictation Management System (ODMS), and Grundig DigtaSoft. However, compatibility can vary by DSS version (DSS Pro vs. standard DSS) and the specific hardware or software version — it is advisable to test a sample file on your target device or application before processing a large batch.
The ADPCM IMA OKI codec used by DSS has very limited configurable parameters — it does not support a quality scale or variable bitrate in the way common codecs like AAC or MP3 do. The codec operates at a fixed low sample rate (typically 8000 Hz) suited to speech. You can attempt to explicitly set the sample rate with '-ar 8000' inserted before the output filename, but the DSS container and codec will constrain the output regardless. There is no meaningful quality dial for this format pair.
On Linux or macOS, you can loop over files in a directory using a shell one-liner: 'for f in *.hevc; do ffmpeg -i "$f" -c:a adpcm_ima_oki "${f%.hevc}.dss"; done'. On Windows Command Prompt, use: 'for %f in (*.hevc) do ffmpeg -i "%f" -c:a adpcm_ima_oki "%~nf.dss"'. This runs the same conversion command sequentially on each HEVC file and outputs a matching DSS file. The in-browser tool handles one file at a time, so the FFmpeg command is especially useful when processing multiple files locally.
Technical Notes
The DSS format was jointly developed by Olympus, Philips, and Grundig as a closed, proprietary standard for portable digital dictation, and FFmpeg's support for it is limited to the ADPCM IMA OKI codec variant at the narrow specifications the format requires. Because HEVC files can carry HDR metadata, 4K or 8K resolution, and high-efficiency audio codecs like AAC or AC-3, none of that richness survives this conversion — only the raw audio PCM samples are decoded and then re-encoded into the ADPCM IMA OKI codec, which uses a simple adaptive delta modulation scheme optimized for the 300–3400 Hz telephony speech band. The DSS container does not support stereo audio in the standard implementation, so any stereo or surround audio in the HEVC source will be downmixed to mono. No metadata from the HEVC file — including creation timestamps, camera model tags, GPS data, or chapter markers — carries over to the DSS output. The output file size will be dramatically smaller than the source HEVC file due to the elimination of video and the extremely low bitrate of ADPCM IMA OKI, often producing files of only a few kilobytes per minute of audio.