Re: [FFmpeg-devel] [PATCH] lavc/libx264: enable x4->params.analyse.b_fast_pskip if mb_info is set

[Stefano Sabatini <stefasab@gmail.com>]

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On date Saturday 2023-09-02 09:20:08 +0000, Carotti, Elias wrote:
> On Thu, 2023-08-31 at 19:09 +0200, Stefano Sabatini wrote:
> > 
> <snip>
> > 
> > > In particular why are you turning on fast_pskip silently based on a
> > > completely different setting?
> > 
> > The patch is fixing the regression introduced by the unconditional
> > setting of b_fast_pskip.
> > 
> > Now the question is if it makes sense to set mb_info without
> > b_fast_pskip (in both case this should be probably documented).
> > 
> > @Elias can you comment about the mb_info/b_fast_pskip use case?
> 
> Sorry again for the delay in responding. 
> We can safely remove it altogether. It's true we don't need to set it
> along with mb_info.
> However, it doesn't do any harm, since fast_pskip is by default set to
> true by libx264 and only turned off either explicitly by the user, or
> when using the placebo preset, or when doing lossless encoding 
> (constant QP == 0.)
> So, I agree, let's remove these three lines.

Thanks, updated.

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From ceb00a939ab2cd0fe146020b0e4e0d80b5d16a5d Mon Sep 17 00:00:00 2001
From: Stefano Sabatini <stefasab@gmail.com>
Date: Fri, 25 Aug 2023 11:35:01 +0200
Subject: [PATCH] lavc/libx264: do not unconditionally set
 x4->params.analyse.b_fast_pskip

Fix output change regression introduced in 418c954e318.
---
 libavcodec/libx264.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/libavcodec/libx264.c b/libavcodec/libx264.c
index ce849d6c9a..cc5e1ba5b1 100644
--- a/libavcodec/libx264.c
+++ b/libavcodec/libx264.c
@@ -1190,7 +1190,6 @@ FF_ENABLE_DEPRECATION_WARNINGS
     }
 
     x4->params.analyse.b_mb_info = x4->mb_info;
-    x4->params.analyse.b_fast_pskip = 1;
 
     // update AVCodecContext with x264 parameters
     avctx->has_b_frames = x4->params.i_bframe ?
-- 
2.34.1


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