JpegSource

Latest revision as of 19:18, 16 June 2020

[edit] Description

An advanced JPEG decoder for AviSynth 2.6 which decodes JPEGs directly in their native colorspace. It supports arithmetic and Huffman encoded JPEGs. In addition, JpegSource has an optional reconstruction pass that can only be done during the decoding stage. This process can accurately suppress common JPEG artifacts (blocking, ringing/mosquito noise, etc). The reconstruction pass is harmless on high quality JPEGs but can produce excellent results on highly compressed JPEGs. This technique yields better results than other post-processing methods.

[edit] Supported Formats

JpegSource supports just about every kind of JPEG file, but due to lack of colorspace support in AviSynth some formats need additional steps to load:

• YUV440 JPEGs - channels have to be loaded individually, see the examples below.
• CMYK/YCCK JPEGs - channels have to be loaded individually.
• RGB encoded JPEGs - to load correctly see the examples below.
• RGB JPEGs other than 4:4:4 have to be loaded manually and converted to a supported format manually.

This may seem cumbersome but the idea of this source filter is to provide the actual encoded data without any colorspace conversions or resizes (these are usually really poor quality in other decoders).
AviSynth colorspace support is quite limited, fortunately most common JPEG formats are natively supported in AviSynth 2.6 (Y8, YV12, YV16, YV24 and YV411).

Remember that JPEGs use PC levels, Rec.601 colorspace and MPEG1 chroma position most of the time. Sadly, there is no way now for source filter to provide such information and you'd have to set correct parameters manually when converting to other colorspaces.

[edit] Requirements

• [x86]: AviSynth+ or AviSynth 2.6
• Supported color formats: Y8, YV12, YV16, YV24, YV411

• SSE2 capbale CPU / SSSE3 capable CPU for reconstruction pass only

[edit] Syntax and Parameters

JpegSource (string file, int "rec", int "channel", int "length", float "fps_num", int "fps_den")

string  file =

Path to image file. Path can be omitted if the script is in the same folder as the image file.

int  rec = 1

Number of reconstruction passes; set to 0 to disable, it's the default if SSSE3 is not supported [1].

Reconstruction pass won't help on recompressed files where artifacts were produced by previous compressions.

int  channel = -1

Load only one image channel with specified index (zero based).

-1 : load all channels

0 : load 1st channel

1 : load 2nd channel

2 : load 3rd channel

3 : load 4th channel (only for CMYK/YCCK JPEGs)

int  length = 1000

Clip length in frames.

float  fps_num = 24

FPS numerator.

int  fps_den = 1

FPS denominator.

[edit] Examples

JpegSource with default settings:

JpegSource("image.jpg", rec=1, channel=-1, length=1000, fps_num=24, fps_den=1)

Correctly display a 4:4:4 RGB encoded JPEG:

JpegSource("RGBimage.jpg")
MergeRGB(last, UToY8(), VToY8(), "RGB24")

Load and convert a 4:4:0 subsampled JPEG to 4:4:4 (YV24):

source = "440image.jpg"

Y = JpegSource(source, channel=0)
U = JpegSource(source, channel=1).Spline36Resize(Y.width(), Y.height())
V = JpegSource(source, channel=2).Spline36Resize(Y.width(), Y.height())

YToUV(U,V,Y)

[edit] Changelog

Version        Date            Changes

2014.4.19      04/19/2010      - Added single-channel mode, so you can load pretty much every JPEG you
                                 can encounter even when Avisynth doesn't have an appropriate colorspace.

2014.4.18      04/18/2014      - Support JPEGs with arithmetic compression.
                               - No longer locks files after first frame was decoded.
                               - Added MT and cache hints for AviSynth+.
                               - Changed compiler to VS2013.

2014.1.5       01/05/2014      - Initial release

[edit] Archived Downloads

[edit] External Links

• Doom9 Forum - JpegSource discussion.
• Subsampling.pdf - pages 3-6 has good information on JPEG subsampling and chroma placement ("centered" and "co-sited").
• Chroma_subsampling_notation.pdf - Page 2 describes JPEG/JFIF, H.261, and MPEG-1 as having the same chroma placement.

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