[FFmpeg-user] Best settings for FFV1

[MrNice]

On 17/09/15 23:45, Dave Rice wrote:
> Hi,
> 
>> On Sep 14, 2015, at 11:56 PM, Etienne Desautels <etienne.desautels at gmail.com> wrote:
>>
>> Hi,
>>
>> I will start using FFV1 to archive video for a museum and I will like to know what's the best settings to get smaller files. I will use version 3 with checksums. From the few tests I did I found that those settings were the best for smaller files:
>>    - coder 1
>>    - context 0
>>    - g 1
> 
> I believe using -g 1 would require more size than not. On the other hand this is usually one of the parameters for ffv1 I recommend the most as it increases the resilience of the file which is particularly relevant for archival use.
> 
>>    - slices 4
>>
>> I really don't know what to think about context size. Somewhere else I saw that large context create smaller files. But in my tests that was the inverse.
>>
>> I also tried 2 pass without any success. The final file were exactly the same size as the one created with 1 pass. And the log of the 2 pass was filled only with 0 except for the last number that was something like 843?
> 
> Can you show your process? Have you tried the directions according to the wiki? http://trac.ffmpeg.org/wiki/Encode/FFV1
> 
> If the file size is a bigger issue than the options used, you could examine the test suite results at http://download.das-werkstatt.com/pb/mthk/ffv1_stats/latest/ <http://download.das-werkstatt.com/pb/mthk/ffv1_stats/latest/>. The labels such as v3c01s4 document the version (3), coder (0), context (1), and slices (4).
> Best Regards,
> Dave Rice
> 
> 
>> Any advices?
>>
>> Regards,
>> Etienne Desautels
>> _______________________________________________

I don't want to interfere but only to understand the parameters.
2nd link, FFv1 results GOP=1 vs. GOP=300

Documentation says:
Slices 	-slices 	4, 6, 9, 12, 16, 24, 30 	Each frame is split into this
number of slices. This affects multithreading performance, as well as
filesize: Increasing the number of slices might speed up performance,
but also increases the filesize.

What I understand in the result, ie: first line
v3c11s4: -16.68% means the resulting file is smaller by this value
compared to the original
v3c11s30: -17.33% means the resulting file is smaller by this value
compared to the original

Conclusion: s30 has a smaller filesize than with s4 (for all the lines)
=> opposite what says the documentation.

Am I right?

BTW what are the default values of all these parameters in the first
link? I can't find any user documentation, I mean not too hard to
understand.