[FFmpeg-devel] [PATCH] avdevice/v4l2enc: Allow writing non-rawvideos to v4l2

[Mark Thompson]

On 26/04/2020 19:08, David Manouchehri wrote:
> This patch allows you to output non-rawvideos to V4L2, which can be quite
> helpful at times when you'd like to offer a compressed source (see example
> usage below).
> 
> ffmpeg -vaapi_device /dev/dri/renderD129 -f v4l2 -input_format yuyv422 -i
> /dev/video2 -f v4l2 -vf 'format=nv12,hwupload' -c:v h264_vaapi /dev/video4
> 
> From ce5f0ebd8e1d40b0f876b0d1b0b0cf564389b874 Mon Sep 17 00:00:00 2001
> From: Roger <roger- at users.noreply.github.com>
> Date: Sat, 4 Nov 2017 16:32:41 -0400
> Subject: [PATCH] avdevice/v4l2enc: Allow writing h264 to v4l2.
> 
> Signed-off-by: David Manouchehri <david.manouchehri at riseup.net>
> ---
>  libavdevice/v4l2enc.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/libavdevice/v4l2enc.c b/libavdevice/v4l2enc.c
> index 1c36f81f90..afbd94f8da 100644
> --- a/libavdevice/v4l2enc.c
> +++ b/libavdevice/v4l2enc.c
> @@ -47,8 +47,7 @@ static av_cold int write_header(AVFormatContext *s1)
>      }
>  
>      if (s1->nb_streams != 1 ||
> -        s1->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO ||
> -        s1->streams[0]->codecpar->codec_id   != AV_CODEC_ID_RAWVIDEO) {
> +        s1->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO) {
>          av_log(s1, AV_LOG_ERROR,
>                 "V4L2 output device supports only a single raw video stream\n");
>          return AVERROR(EINVAL);
> @@ -56,7 +55,7 @@ static av_cold int write_header(AVFormatContext *s1)
>  
>      par = s1->streams[0]->codecpar;
>  
> -    v4l2_pixfmt = ff_fmt_ff2v4l(par->format, AV_CODEC_ID_RAWVIDEO);
> +    v4l2_pixfmt = ff_fmt_ff2v4l(AV_PIX_FMT_NONE, s1->streams[0]->codecpar->codec_id);

I think you only want NONE for non-RAWVIDEO - the raw formats still need to be mapped.

>      if (!v4l2_pixfmt) { // XXX: try to force them one by one?
>          av_log(s1, AV_LOG_ERROR, "Unknown V4L2 pixel format equivalent for %s\n",
>                 av_get_pix_fmt_name(par->format));
> -- 
> 2.17.1
> 

Seems like a nice change!

Thanks,

- Mark