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Hardware acceleration and fingerprinting

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#896 2 comentarios 5 reacciones 0 asignados Ver en GitHub

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Evaluación

Dificultad
5/5
Tiempo estimado
Más de una semana
Aptitud para principiantes
30/100
Tipo de issue
Nueva funcionalidad
Claridad
Bastante claro
Estado de actividad
Estancado
Stack tecnológico
javascript
Área
api, audio-video-rtc

Línea de trabajo

Comienza por la sección sobre aceleración por hardware de la especificación de WebCodecs y el ejemplo de VideoEncoder.isConfigSupported; después, revisa el informe de Bugzilla enlazado y los dos comentarios existentes. La issue estará terminada cuando se hayan acordado y especificado el comportamiento de hardwareAcceleration bajo restricciones de fingerprinting y el resultado observable para los autores.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

I just filed a bug on Bugzilla but what Firefox is doing is spec compliant, so I wanted to raise the issue here too.

Background

I'm making a website that heavily utilizes WebCodecs. I need to determine the encoding codec and always want to use hardware encoding (when available) as battery life is more important than fidelity (conference call).

  1. Loop through all codecs in order of network efficiency: av1, vp9, hevc, h254, vp8, etc
  2. Check if the browser supports hardware acceleration, if so return it.
  3. Repeat the loop but this time with software acceleration.

I'm using the hardwareAcceleration: "prefer-hardware" field to determine if hardware acceleration is supported. Here's an example of one of the checks:

VideoEncoder.isConfigSupported({
    codec: "av01.0.08M.08",
    width: 1280,
    height: 720,
    hardwareAcceleration: "prefer-hardware",
}).then(console.log)

Here's a little modal I created to visualize the process and the results on my M2 laptop and Chrome.

Image

Problem

Here's what Firefox reports:

Image

Ignore the partial support for video capture (MediaStreamTrackProcessor polyfill).

The problem is that Firefox is reporting hardware acceleration for AV1, VP9, etc. So my encoder will naively select one of those codecs and suddenly my CPU is on fire.

My guess is that Firefox is ignoring the hardwareAcceleration field to avoid fingerprinting. Here's the relevant section in the specification:

If a User Agent does not implement [media-capabilities] for reasons of fingerprinting, they SHOULD ignore the HardwareAcceleration preference

Proposed

If the browser won't respect hardwareAcceleration because it can be used for fingerprinting, then the browser should return an error somehow. I don't think the browser should silently ignore important configuration values without feedback.

If I knew that Firefox doesn't allow probing for hardware acceleration, then I would use H.264 because hardware acceleration is very common and easier on the CPU. Then I could also report hardware acceleration as "unknown" and maybe show a modal explaining why performance might be poor.

My suggestions:

  1. Don't return hardwareAcceleration in the config returned by isConfigSupported. Unfortunately, this isn't quite correct, as hardwareAcceleration is supported but only as a hint.
  2. Add "require-hardware" and "require-software" as options, throwing an exception (or returning false?) if they are used on browsers that care about fingerprinting.
  3. Firefox pls allow me to detect hardware acceleration. Otherwise I can't use newer codecs for fear of melting silicon.

I think #2 is the best option. It's kind of strange that Chrome returns isConfigSupported=false when "prefer-hardware" is used. If it's just a hint, like the "prefer" implies, then it should always return true if either software or hardware encoding is available... right?

Lenguaje dominante
HTML
Estrellas
1.3k
Forks
192
Merge medio
3 h 36 min
PR fusionados (30 d)
7

Preparar el entorno

Primeros pasos

  1. Lee el issue completo y luego la guía de contribución del proyecto.
  2. Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

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