Codecs
Quasar supports H.264, HEVC and AV1, one per session, chosen by the server at launch. Leave the codec on Auto and pick a quality tier: the server matches it to what the host’s GPUs can encode and your browser can decode.
Choosing one yourself
Section titled “Choosing one yourself”Launch options ▸ Codec in the launch panel lists only codecs this device can decode and some eligible GPU can encode. On Auto, the server prefers a free GPU that can give your device its best codec.
A codec you pick is a requirement and is never downgraded. If a GPU that encodes it is busy, the launch waits. If no online GPU can encode it, the launch is refused with a message naming the codec.
A host’s codecs depend on its encoder. See Encoders.
What each one buys you
Section titled “What each one buys you”| Codec | Catalog bitrate target | Decodes in Chrome |
|---|---|---|
| H.264 | Baseline | Browser-session fallback |
| HEVC | 30 to 40% lower | Only with OS hardware decode |
| AV1 | 40 to 50% lower | When the browser reports support; software decode may be used |
These are the shipped catalog’s targets, not a guarantee of equal quality. A better codec buys bandwidth headroom, not latency: it matters on a constrained link, barely at all on a clean LAN.
How the server picks
Section titled “How the server picks”A quality tier is an ordered list of encode rungs. The server takes the first rung that passes four checks:
- The session’s GPU can encode it. Each GPU offers HEVC or AV1 only after a short test encode passes, so a freshly started host offers H.264 alone for a few seconds.
- The client can decode it. Measured at login and stored per device. HEVC and AV1 need a positive result; a missing or stale measurement means neither.
- It hasn’t failed for this client before.
- Hardware encode is available, where the rung requires it.
Every shipped tier ends in an H.264 rung as a compatibility fallback. A launch still needs an eligible host and a working client. The default order is AV1, then HEVC, then H.264.
HEVC in Chrome
Section titled “HEVC in Chrome”Chrome decodes HEVC only with OS hardware decode. No software fallback.
| Client | HEVC |
|---|---|
| macOS | Almost always |
| Windows | Usually, depending on the GPU |
| Linux | Effectively never |
Linux clients get the next rung down. Headless Chrome on Linux never offers HEVC, so testing HEVC needs a real browser on macOS or Windows.
AV1 availability is checked per device. A browser may use software decoding when hardware decoding is unavailable, which increases client CPU use. Select H.264 if AV1 playback is not smooth on your device.
H.264 profile
Section titled “H.264 profile”Browser sessions use the constrained-baseline profile, because Chrome fails to decode High profile H.264 from AMD and NVIDIA hardware. Nothing to configure, but it’s why browser H.264 looks worse at a given bitrate. Main and High need a native client.
Turning codecs on
Section titled “Turning codecs on”The codec is a property of a stream profile. Edit it in the stream profile’s drawer under Admin ▸ Streaming ▸ Stream profiles. Launch profiles order those rungs, best first, and that order is the preference. The shipped profiles already include HEVC and AV1. A launch profile with no H.264 rung is rejected.
The catalog says hevc; the wire and session records say h265. Same codec.
Checking what a session used
Section titled “Checking what a session used”Admin ▸ Sessions, session detail, shows the resolved codec. If it’s not what you expected, one of the four checks above failed, usually the client’s decode measurement.