[Cellar] Robert Wilton's No Objection on draft-ietf-cellar-ffv1-17: (with COMMENT)
Robert Wilton via Datatracker <noreply@ietf.org> Mon, 05 October 2020 14:54 UTC
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Date: Mon, 05 Oct 2020 07:54:36 -0700
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Subject: [Cellar] Robert Wilton's No Objection on draft-ietf-cellar-ffv1-17: (with COMMENT)
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Robert Wilton has entered the following ballot position for draft-ietf-cellar-ffv1-17: No Objection When responding, please keep the subject line intact and reply to all email addresses included in the To and CC lines. (Feel free to cut this introductory paragraph, however.) Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html for more information about IESG DISCUSS and COMMENT positions. The document, along with other ballot positions, can be found here: https://datatracker.ietf.org/doc/draft-ietf-cellar-ffv1/ ---------------------------------------------------------------------- COMMENT: ---------------------------------------------------------------------- Hi, Thank you for taking the time to document FFV1 version 0, 1 and 3. I support Barry's discuss in that I found this document hard to read and interpret. I think that I would struggle to implement a FFV1 encoder/decoded from scratch based on this document. However, this is a long way outside my area of expertise and there is perhaps a corpus of basic video codec knowledge that is assumed in this specification. Is the intention of this document that it gets obsoleted when FFV1 version 4 is documented? I haven't reviewed the entirety of this document, but I do have some comments of particular areas of the document that I found hard to follow that additional text or explanation may be helpful. Overall, having some more introduction text explaining the overall structure of the encoding , i.e. how the different parts fit together would likely help readability. 3.1. Border Figure 2: A depiction of FFV1's assumed border for a set example Samples. I wasn't sure whether an extra row at the bottom of this table would have been helpful, but perhaps it is not required because it is not referenced. 3.2. Samples The labels for these relative "Samples" are made of the first letters of the words Top, Left and Right. Don't feel obliged to change this, but I wonder whether keep lowercase for all of the relative positions might have been clearer. E.g., perhaps using "tt" instead of "T" and "ll" instead of "L". 3.3. Median Predictor Exception for the median predictor ... Possibly putting the exception text into a 3.3.1 sub-section would aid readability. 3.4. Quantization Table Sets It wasn't clear to me what a "Quantized Sample Differences" is. 3.7.2. RGB Cb = b - g Cr = r - g Y = g + (Cb + Cr) >> 2 g = Y - (Cb + Cr) >> 2 r = Cr + g b = Cb + g Perhaps split into two sets of 3 equations to define the relationship in either direction. Exception for the JPEG2000-RCT conversion ... Again, putting this into a sub-section (3.7.2.1) might aid readability, i.e. the split between what is desired vs what is being described due to bugs in real implementations. 3.8. Coding of the Sample Difference coder_input = [(sample_difference + 2 ^ (bits - 1)) & (2 ^ bits - 1)] - 2 ^ (bits - 1) It wasn't clear to me what [] brackets meant here. 3.8.1.1. Range Binary Values I found this hard to follow, as in I couldn't figure out what it means. 3.8.1.4. State Transition Table It wasn't really clear to me what these were used for. 3.8.2.1. Signed Golomb Rice Codes Unclear what is meant by "ESC case" Regards, Rob
- [Cellar] Robert Wilton's No Objection on draft-ie… Robert Wilton via Datatracker
- Re: [Cellar] Robert Wilton's No Objection on draf… Jerome Martinez
- Re: [Cellar] Robert Wilton's No Objection on draf… Spencer Dawkins at IETF
- Re: [Cellar] Robert Wilton's No Objection on draf… Michael Richardson
- Re: [Cellar] Robert Wilton's No Objection on draf… Spencer Dawkins at IETF
- Re: [Cellar] Robert Wilton's No Objection on draf… Rob Wilton (rwilton)
- Re: [Cellar] Robert Wilton's No Objection on draf… Jerome Martinez
- Re: [Cellar] Robert Wilton's No Objection on draf… Michael Richardson