[FFmpeg-devel] [PATCH] avdevice: add fbdev output device

[Lukasz M]

On 22 October 2013 20:04, Stefano Sabatini <stefasab at gmail.com> wrote:

> > It is offtopic, I will probably come back with it later as RFC or
> something.
> > In general I mean that codec may support all formats but output device
> only
> > few of them.
> > If device provide list of supported formats aside the codec formats list,
> > then proper format
> > may be chosen without user intaraction and without "guessing" basing on
> > both list.
> > I haven't analyse code so these are just simple thoughts, not sure it is
> > applicable.
>
> Some devices support some combinations of formats/codecs (typically
> rawvideo + a few supported formats), but I can think of output devices
> accepting accepting encoded packets, thus you should probably consider
> codec/format couples.
>
> I'm not sure if automatic choice can be fully automated (probably yes).
>

OK, thanks for adive. I will come back to it in some time


>
> > +    if (ioctl(fbdev->fd, FBIOGET_VSCREENINFO, &fbdev->varinfo) < 0)
> > +        av_log(h, AV_LOG_WARNING,
> > +               "Error refreshing variable info: %s\n", strerror(errno));
>
> Note: strerror() is not thread-safe, please use av_str2err(AVERROR(errno))


I missed that one. Fixed in attached patch.


> > +
> > +    pix_fmt = get_pixfmt_from_fb_varinfo(&fbdev->varinfo);
> > +
> > +    if (pix_fmt != fbdev->pix_fmt) {
> > +        av_log(h, AV_LOG_ERROR, "Pixel format %s is not supported, use
> %s\n",
> > +               av_get_pix_fmt_name(fbdev->pix_fmt),
> av_get_pix_fmt_name(pix_fmt));
> > +        return AVERROR(EINVAL);
> > +    }
>
> The logic and error message is a bit misleading. In case pixel format
> changes dynamically it could be != fbdev->pix_fmt and still be a valid
> pixel format. So you should probably first check in case you get
> pix_fmt == NONE.
>
> Alternatively you fail if you notice that the pixel format changes.
>

I think you misread this. fbdev->pix_fmt contained provided stream's pixel
format.
In case pix_fmt obtained from fb_varinfo is different than stream's format
then conversion would be required.
It doesn't matter pixel format obtained from fb_varinfo is supportable or
not when it is different then stream's one.

I can't remember why I put video information in private context, but it is
not required.
I changed them to local variables and made variable names more descriptive.
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