5 ms·

> 4K at 30 Hz (H.264/H.265) and 60 Hz (M/JPEG) supported I am greatly amused at the thought of 2160p60 MJPEG. That must be extremely efficient…

cmrdporcupine 9y ago
I chuckled at that, too. I struggle to imagine what would be on the receiving end of that. I doubt most desktop machines could decode a 60fps 4k MJPEG stream, let alone a phone. Maybe they sell an SOC the other side too.
- yeureka 9y ago
  Any desktop would be able to do so. I wrote a multi stream mjpeg decoder some years ago and it could run three MJPEG streams at 1920x1080@30 on a 2008 Macbook Pro (Core 2 Duo, 2.5ghz ).
  - deleted 9y ago
    [deleted]
  - userbinator 9y ago
    That's only ~187MP/s. A single 4k 2160p60 stream needs almost 500MP/s, which might be at the edge of what's possible on a CPU today, but would make far more sense for a GPU to do.
    - wtallis 9y ago
      It shouldn't be a stretch for a quad-core desktop processor today. Doubling the core count and increasing clock speed by 40% compared to a mobile Core 2 isn't hard. DDR4 instead of DDR2 means memory bandwidth is probably not an issue, and AVX can probably provide further headroom on the compute power. And, of course, it's much easier to build a desktop with far more than four CPU cores these days.
- userbinator 9y ago
  JPEG, and by extension MJPEG, is far simpler to decode than most video codecs, and also massively parallelisable. 4k at 60FPS is less than 500MP/s, which is easily achievable by a GPU.
  - cmrdporcupine 9y ago
    Sorry, but I've benchmarked this recently as part of a project that I'm working on, and JPEG decoding with libjpeg-turbo consumed far more CPU than software H.264 decoding. The encoding side is very expensive with H.264, but as I understand it a lot of work goes into building the right reference frames so that higher compression and faster decode can be achieved.
    - rubatuga 9y ago
      You are comparing CPUs to GPUs right now
      - nickpeterson 9y ago
        Is that the new apples to oranges?
      - sheepdestroyer 9y ago
        he said software x264, so CPU to CPU?
        sand500 9y ago
        It may be different when comparing GPU to GPU because of difference in parallelization
jdietrich 9y ago
MJPEG is a common encoding format for computer vision cameras. The artifacts associated with inter-frame compression is perfectly tolerable for humans, but it can completely stymie a lot of CV applications. High-efficiency video codecs rely on motion prediction to reduce file size - fine for watching Game of Thrones, but a disaster if you're a motion tracking algorithm. Given the target market for this chip, it's a perfectly logical and highly useful feature.
- deleted 9y ago
  [deleted]
Matthias247 9y ago
The reason for these kind of codecs is also often latency. Efficient H.264 encoding (with B-frames and P-frames) has lots of it. For realtime applications usually a low latency is required.

cmrdporcupine 9y ago

I chuckled at that, too. I struggle to imagine what would be on the receiving end of that. I doubt most desktop machines could decode a 60fps 4k MJPEG stream, let alone a phone. Maybe they sell an SOC the other side too.

yeureka 9y ago
Any desktop would be able to do so. I wrote a multi stream mjpeg decoder some years ago and it could run three MJPEG streams at 1920x1080@30 on a 2008 Macbook Pro (Core 2 Duo, 2.5ghz ).
- deleted 9y ago
  [deleted]
- userbinator 9y ago
  That's only ~187MP/s. A single 4k 2160p60 stream needs almost 500MP/s, which might be at the edge of what's possible on a CPU today, but would make far more sense for a GPU to do.
  - wtallis 9y ago
    It shouldn't be a stretch for a quad-core desktop processor today. Doubling the core count and increasing clock speed by 40% compared to a mobile Core 2 isn't hard. DDR4 instead of DDR2 means memory bandwidth is probably not an issue, and AVX can probably provide further headroom on the compute power. And, of course, it's much easier to build a desktop with far more than four CPU cores these days.
userbinator 9y ago
JPEG, and by extension MJPEG, is far simpler to decode than most video codecs, and also massively parallelisable. 4k at 60FPS is less than 500MP/s, which is easily achievable by a GPU.
- cmrdporcupine 9y ago
  Sorry, but I've benchmarked this recently as part of a project that I'm working on, and JPEG decoding with libjpeg-turbo consumed far more CPU than software H.264 decoding. The encoding side is very expensive with H.264, but as I understand it a lot of work goes into building the right reference frames so that higher compression and faster decode can be achieved.
  - rubatuga 9y ago
    You are comparing CPUs to GPUs right now
    - nickpeterson 9y ago
      Is that the new apples to oranges?
    - sheepdestroyer 9y ago
      he said software x264, so CPU to CPU?
      - sand500 9y ago
        It may be different when comparing GPU to GPU because of difference in parallelization

jdietrich 9y ago

MJPEG is a common encoding format for computer vision cameras. The artifacts associated with inter-frame compression is perfectly tolerable for humans, but it can completely stymie a lot of CV applications. High-efficiency video codecs rely on motion prediction to reduce file size - fine for watching Game of Thrones, but a disaster if you're a motion tracking algorithm. Given the target market for this chip, it's a perfectly logical and highly useful feature.

deleted 9y ago
[deleted]

Matthias247 9y ago

The reason for these kind of codecs is also often latency. Efficient H.264 encoding (with B-frames and P-frames) has lots of it. For realtime applications usually a low latency is required.