Tagged with jpeg - Personal View Talks

MJPEG Audio Sample Rate and Bitrate on GF1 (maybe other cameras too)

DidiEdd — Mon, 19 Aug 2024 12:35:05 +0000

Hey there, thanks for the ptool hack Vitaly, I've been using it for over half a year now and I'm finally starting to realize its full potential on my GF1 after understanding more about cameras and picture/video data in general, so it's been a big help in regards to my camera hobby, specifically with recording video on a camera not-so-good for video.

But eventually I realized a minor issue as well. This is regarding the audio of MJPEG (on GF1, but maybe other cameras as well). For some reason, when recording MJPEG, the audio bitrate is just okay at 256/257/268/281 kbps. However, the worse issue is that it is being captured at 16,000 samples per second, which is an issue because essentially any frequency past 8 KHz cannot be recorded to the video... With AVCHD Lite, the audio is successfully recorded at a high bitrate of 448 kbps, but even more importantly, the sample rate is 48,000 Hz which can capture frequencies up to 22 KHz safely. I want to make use of MJPEG at times, but with this knowledge I have to be careful not to use it in situations where the audio could be important (considering I have to use my phone as an external mic). It takes time to get my other audio sources running, so in a "quick, record!" moment, I wouldn't want to be forced to use AVCHD Lite in a situation where I would've preferred to use MJPEG, just because the audio will be poor for the time it takes to enable my external audio recording setup.

From what I've seen on the site nowadays, I've gathered that you've done something along the lines of "retiring" from this ptool project, so I understand if there's nothing you can do, but if possible, couldn't there be any way we could get the sample rate fixed to 48 KHz for MJPEG and not just AVCHD? Additionally, for the bitrate settings to affect MJPEG as well, not just AVCHD. Thank you for your time.

It happened in our time... The AI singularity arrives to resurrect low light pictures.

duartix — Tue, 15 May 2018 09:32:41 +0000

A JPEG Engine to rule them all? Or one definitive step closer to the Great AI Takeover? You decide...

https://arxiv.org/pdf/1805.01934v1.pdf

BPG (Better Portable Graphics) image format based on HEVC intra frame encoding

karl — Tue, 28 Apr 2015 15:49:25 +0000

Fabrice Bellard (of ffmpeg, Qemu and other fame) has proposed and provides a free implementation of a still image format and codec based on the HEVC video codec standard.

BPG (Better Portable Graphics) is a new image format. Its purpose is to replace the JPEG image format when quality or file size is an issue. Its main advantages are:

High compression ratio. Files are much smaller than JPEG for similar quality.

Supported by most Web browsers with a small Javascript decoder (gzipped size: 56 KB).

Based on a subset of the HEVC open video compression standard.

Supports the same chroma formats as JPEG (grayscale, YCbCr 4:2:0, 4:2:2, 4:4:4) to reduce the losses during the conversion. An alpha channel is supported. The RGB, YCgCo and CMYK color spaces are also supported.

Native support of 8 to 14 bits per channel for a higher dynamic range.

Lossless compression is supported.

Various metadata (such as EXIF, ICC profile, XMP) can be included.

Animation support.

Find the description, details and links at bellard.org.

For an online comparison of BPG with other still image codecs have a look at this demo.

BTW: Meanwhile, the Daala development team is still struggling to achieve intra-frame encoding on par with HEVC without using patent-encumbered technology.

Exporting movie with Motion Jpeg Codec with After Effects CC (Mac)

x_worpig_x — Thu, 12 Dec 2013 18:38:18 +0000

Hey guys, I'm currently using After Effects CC at work on an iMac 27". I have to render out a video in .MOV Motion Jpeg that will be playing at a local Cineplex theatre, but I can't find the codec anywhere... Any suggestions?

GH2 files to PHOTO JPEG

miza — Tue, 03 Apr 2012 05:22:41 +0000

Hello, I have a big problem converting files after editing to PHOTO JPEG. Even if I choose the best settings the quality is really bad. There is a lot of aliasing which is not so visible on the original file?

I'm using Windows and Premiere pro CS5. The same thing was on Apple and Final Cut.

Is there any solution to that? I must have PHOTO JPEG as an output.

Here is a sample picture: http://shrani.si/f/g/a5/vhSletJ/test-gh2.jpg

Thanks for the help

JPEG estimator and quantization

Vitaliy_Kiselev — Thu, 25 Aug 2011 18:29:59 +0000

New interesting article about company

Q: How does the JPEG format works?

A: JPEG is a lossy compression, meaning that any JPEG compression involves some loss of information. The compression consists of several steps:

•Color space transformation from RGB to YCBCR
•Reducing the spatial resolution of the CB and CR components by a factor of 2 in the horizontal axis, or both in the horizontal and the vertical axis (this step is optional).
•Dividing each color components to blocks of 8×8 pixels.
•Transforming each 8×8 block to the frequency domain using a DCT transform.
•Quantization (reduction of precision by representation with a lower number of bits) of each of the frequency components using a quantization matrix. This is the main stage that causes loss of information.
•Entropy coding (a lossless compression, similar to ZIP) on the frequency components which have undergone quantization.

Q: Is saving an image in Photoshop in minimum JPEG compression (i.e. 12) lossless?

A: Even at quality 12, the Photoshop quantization matrix has values which are greater than 1, so the precision of some of the frequency components is reduced, meaning that some information is lost (you can view the quantization matrixes for Photoshop’s quality 12 here).

Actually, even when using a quantization matrix that has all values set to 1, there is a loss of quality due to the DCT transform and the conversion from floating point values to integer values.

Read the rest at: http://www.megapixel.co.il/english/archive/21907

Other interesting read on JPEGSnoop author page:

http://www.impulseadventure.com/photo/jpeg-quantization.html

http://www.impulseadventure.com/photo/jpeg-huffman-coding.html

GH2 MJPEG 1080p 25 fps.

Athiril — Mon, 12 Dec 2011 07:00:37 +0000

Odd. Last time I tried the Change fps function for MJPEG it just fubar'ed all the time.

Now I went to stock settings (original GH2) for MJPEG with 25 fps, worked. So loaded the LPOWELL 100mbps/night 1080p settings, added 25 fps changed, works on my GH2. I'm not sure if it's merely dropping 5 frames out of every second (don't think it is). But if you shoot 1/25th, not sure if that it'd matter?

I'll try to examine it at some point with some linear motion at fixed speed, and look for 'jumps' in space.

My test file is reported as 75,697 kbps. Or 74 mbps. Which would be 88.7 mbps @ 30 fps, at the same average size/compression per frame. Available recording time is reported as 3m 12s. Recording on a Transcend 32gb class 10.

Test file was shot at ISO 2500, probably a stop underexposed still by the looks, just messing around in indoor light.

I'll do some slow panning on a monopod tomorrow with shutters @ and greater than 1/30th, and upload that.

Also I have gotten sizes a bit above 1080p working fine before too, which is useful I think for stabilising software if (such as deshaker) if you can shooter slightly wider than you want/need, so you don't have to blow up (or blow up as much) back to 1080p frame size for a 1080p output workflow. Combined with 25 fps would be great.