Dali Compare is a simple but unique application designed to visually represent the quality of your video conversions
Drag-and-drop a source clip into the Master Clip panel, then drag-and-drop a video conversion from that clip into the Comparison Clip panel and "Compare!".
Dali Compare then processes the two clips and creates an A-B mix from both. When you establish a 50/50 mix of any original digital signal with a negative image of the same signal - the resulting visual differences are the errors generated by the conversion encoding. A blank image with no notable visual differences indicates a very high degree of quality and accuracy in the process
Fig 1 - example of high-quality conversion analysis
Fig 2 - example of highly compressed conversion analysis
Fig 3 - Original clip
Both analysis examples above were generated from conversions of the same source clip (Fig 3) - Fig 1 shows the analysis of a ProRes 4:4:4 conversion - Fig 2 shows the analysis of an MP4 conversion with heavy compression. Notice how the Fig 1 shows no discernible detail - this indicates that there is a very close match between the compared clips. The analysis in Fig 2 shows serious compression artifacts as well as color mismatch due to low bitrate and low-quality codec rendering
The more color detail visible in the comparison, the less quality of conversion when compared to the original clip
Dali Compare provides unique tools for checking conversion quality. Here's how it works:
Note that no colors present indicates very high fidelity of color conversion - the dark areas in the analysis indicate the conversion from 4:2:0 to 4:4:4 color space and interpolation (which fills in the missing colors between color spaces) - this is a good thing ; )
In addition, Dali Compare provides PSNR (Peak Signal to Noise Ratio) and SSIM data for quality evaluation of both clips under comparison
The bottom left viewer shows the source clip (clip 1) and scrollbar. Use this to scrub through both clips to select frames for comparison
Use the Zoom to scrutinize fine detail and use the color info to compare color rendition
Once an analysis is complete you can play the comparison video itself via the button on the main interface
You will also find icons at the bottom of the scopes panel for grabbing full-size TIFF images from the frame currently in view - one for each clip in the viewer
Note - when running a comparison analysis, scrolling in the scope panel is disabled - once the comparison is completed control will return
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A Note About Sound
Compare Oranges to Oranges...
In order to keep your conversion analyses honest, it is best to setup the conversion (to be tested) - to convert without audio. Some audio formats actually embed a time offset in the video clip in order to maintain audio / video sync throughout the converted video. This may cause a delay in the first frame - which will in turn offset the analysis and consequently show false positives
You may notice a slight difference in the durations shown for source clip opposed to comparison clip. This is also an audio artifact - it is common for and audio track not to match 100% with the last video frame - causing a slight discrepancy in durations. This time should be within merely hundredths of a second - larger discrepancies may indicate other transcoding problems (extra frames, wrong framerate, etc.
Example of analysis with audio offset error
Dali Compare is free to use for any purpose and does not require license