CONVERT GSM → OPUS (GSM to OPUS)
Fast, secure GSM to OPUS conversion. No registration required.
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HOW TO CONVERT GSM → OPUS
Upload the GSM
Drop or select your GSM file. The upload is encrypted and the file is queued for conversion.
Transcode via FFmpeg
FFmpeg decodes the GSM stream to PCM internally, then re-encodes as OPUS at the bitrate you select.
Download the OPUS
The OPUS is delivered as a direct download; metadata and cover art transfer automatically where possible.
Why this pair exists — GSM is an audio format with specific trade-offs between file size, bitrate flexibility, and device support. Ergo, the OPUS route. Need a OPUS version of a GSM recording for a podcast host, audio book platform or DAW that refuses the original container? Drop the file above and our encoder produces a clean OPUS you can drag straight into the destination tool. Metadata such as title, artist and cover art travels with the audio. Technical note: GSM is an audio format with specific trade-offs between file size, bitrate flexibility, and device support. Compare that with Opus is the modern low-latency royalty-free codec used in VoIP, streaming, and WebRTC.
Why convert GSM to OPUS
GSM Audio is great in its own niche, but Opus Audio is either more universally playable or better suited to the device you are targeting. Converting lets you ship the audio without asking listeners to install a codec. The loss in quality between the two is negligible at sensible bitrates.
GSM vs OPUS — Technical specifications
Side-by-side comparison of the technical details.
GSM
- MIME type
- audio/gsm
- Extension
- .gsm
- Codec
- GSM 06.10 (RPE-LTP)
- Sample rate
- 8 kHz
- Bitrate
- 13 kbps
- MIME Type
- audio/gsm
- Category
- Audio Files
- Full Name
- GSM Audio
- Conversion Engine
- FFMPEG
OPUS
- MIME type
- audio/opus
- Extension
- .opus
- MIME Type
- audio/opus
- Category
- Audio Files
- Full Name
- Opus Audio
- Conversion Engine
- FFMPEG
- Extensions
- .opus, .ogg (container)
- Standard
- RFC 6716 (2012)
- Sample rates
- 8, 12, 16, 24, 48 kHz
- Latency
- 5-60 ms (configurable)
| Specification | GSM | OPUS |
|---|---|---|
| MIME type | audio/gsm | audio/opus |
| Extension | .gsm | .opus |
| Codec | GSM 06.10 (RPE-LTP) | — |
| Sample rate | 8 kHz | — |
| Bitrate | 13 kbps | — |
| MIME Type | audio/gsm | audio/opus |
| Category | Audio Files | Audio Files |
| Full Name | GSM Audio | Opus Audio |
| Conversion Engine | FFMPEG | FFMPEG |
| Extensions | — | .opus, .ogg (container) |
| Standard | — | RFC 6716 (2012) |
| Sample rates | — | 8, 12, 16, 24, 48 kHz |
| Latency | — | 5-60 ms (configurable) |
GSM vs OPUS — Strengths and limitations
What each format does best, and where it falls short.
GSM Strengths
- Tiny bitrate (13 kbps) — hours of speech in a few MB.
- Speech-optimized — clear voice reproduction.
- Universal cellphone decoder adoption 1991-2015.
- Stable since 1987.
Limitations
- Speech-only — music sounds distorted.
- 8 kHz sampling — narrowband, muffled by modern standards.
- Legacy — LTE VoLTE moved to AMR-WB, Opus, or EVS.
OPUS Strengths
- Best-in-class quality across the entire bitrate range.
- Royalty-free and patent-free.
- Ultra-low latency — suitable for live voice and music.
- Handles speech and music equally well — no need to switch codecs.
- Mandatory codec in WebRTC, so supported in every browser by design.
Limitations
- Very low hardware decoder adoption — software-only on most phones.
- Older platforms (legacy Windows apps, old cars) may not play .opus files.
- Container semantics confusing — Opus lives inside Ogg, WebM, or MP4.
Quality & Compatibility
Lossy-to-lossy transcoding (most cross-format audio jobs) loses a tiny amount of quality on each pass — usually inaudible at our default VBR ~190 kbps for music or 96 kbps for speech. Lossy-to-lossless conversions freeze the existing quality but cannot improve it; lossless-to-lossy is only as good as the target bitrate you choose.
Tips for Best Results
- Pick 128 kbps for podcasts and voice, 192–256 kbps for music, 320 kbps only if the audio will be edited further downstream.
- Keep the GSM master alongside the OPUS — re-encoding a lossy format twice accumulates audible artefacts.
- For mono voice content, convert to mono OPUS explicitly to halve file size without any quality loss.
Frequently Asked Questions
Lossy-to-lossy conversions (most combinations) re-compress the audio, which technically introduces some loss. At a 192 kbps or higher target it is inaudible on normal equipment. Lossy-to-lossless conversions freeze the existing quality but cannot improve it; lossless-to-lossy transcodes are only as good as the target bitrate you choose.
For voice content (podcasts, audiobooks, lectures) 128 kbps is indistinguishable from higher bitrates. For music, 192-256 kbps covers most listening; 320 kbps is the ceiling for OPUS and the right choice for audio you plan to edit further. Above that, prefer a lossless target instead.
Yes. Title, artist, album, year and cover art travel from the GSM container to the OPUS container automatically where both formats support them. If a tag field has no OPUS equivalent, it is dropped silently. Use any tag editor (Mp3tag, MusicBrainz Picard) to fine-tune afterwards.
GSM Audio
Source formatGSM 06.10 is a speech compression standard designed for the Global System for Mobile Communications. It encodes speech at 13 kbps using Regular Pulse Excitation with Long Term Prediction, optimized for voice intelligibility over cellular networks.
Opus Audio
Target formatOpus is a versatile, open-source audio codec optimized for both speech and music at very low bitrates. It is the standard for WebRTC voice calls and excels at real-time communication.
Going the other way? Convert OPUS back to GSM with the same engine.
Common Use Cases
Share across platforms
Send OPUS files to anyone without worrying about whether they have the right software for GSM.
Embed in documents
Drop OPUS output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
OPUS often produces smaller files than GSM for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
GSM vs OPUS — Typical file sizes
Approximate file sizes for common scenarios.
- 1 min of voice ~100 KB
- 1 hour voicemail archive ~6 MB
- Voice call (24 kbps) 180 KB/min
- Podcast (48 kbps) 21 MB/hour
- Music (128 kbps) ~1 MB/min
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Related comparisons
See these formats side by side to understand which fits your use case best.
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