>From: "Ronald S. Bultje" <rsbul...@gmail.com>
>Hi, 
>
>On Mon, Apr 23, 2018 at 2:10 AM, Karthick J <mailto:kjeya...@akamai.com> wrote:
>>-    int level = par->level == FF_LEVEL_UNKNOWN ? 0 : par->level;
>>+    int level = par->level == FF_LEVEL_UNKNOWN ?
>+        get_vp9_level(par, frame_rate) : par->level;
>
>
>After this change, how will I create a file without a level?
For best player side behavior, you shouldn't create a file without a level. 
Theoretically level is meant to signal the player, a maximum decoder complexity 
required to play the encoded content. Ideally the player should compare the 
stream's level with its maximum VP9 level supported by the device to decide if 
the device is capable of playing the current VP9 stream. 
If we set this to 0, based on the player implementation it will either take it 
as invalid or will assume the stream has a level lower than the device's 
maximum supported level. 
Hence setting the level more accurately is always better than setting it as 0, 
for best player side experience. Also, as James mentioned 0 is not mentioned in 
the spec as "unknown" or "unspecified".
>
>This patch blurs the line between "unknown", "unspecified", "non-existent" and 
>"autodetect". Linguistically, each of these mean something fundamentally 
>different. I think it's acceptable to not have too many ways of specifying 
>something which in practice comes down to >"nope", but you're removing the 
>"nope" altogether, which isn't quite right either.

>
>Ronald 

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