[FFmpeg-user] Warning: data is not aligned! This can lead to a speedloss

Moritz Barsnick barsnick at gmx.net
Wed Oct 18 19:11:51 EEST 2017

On Wed, Oct 18, 2017 at 15:56:17 +0000, Ganesh.Irelan at syda.org wrote:
> The following command seems to execute fine with no perceptible loss in audio sync but there is a warning issued: [swscaler @ 0x7ffc8a823800] Warning: data is not aligned! This can lead to a speedloss.
>   What is causing it and how can I eliminate it?

It means that one of the input or output dimensions when scaling is not
multiple of 16. Thereby, the accelerated scaling code (e.g. via MMX or
SSE) will not behave in an optimal manner (i.e. may be slower). IMHO,
it's nothing you should worry about nor anything you would do something

It does sometimes hint at another issue: If the final dimensions aren't
multiples of 8, 16, 32 (depending on codec), the codec may behave
suboptimally. So you need to choose your target size wisely sometimes.
This is not an issue in your quoted case though.

> ffmpeg version 3.1.1-tessus Copyright (c) 2000-2016 the FFmpeg developers

This version is quite old. If you use a newer one, one of your other
warnings will go away, namely this one:

> [mp4 @ 0x7ffc8b026800] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.


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I feel privileged now! :-) (We are all addressees, alas.)

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