L'octidi 28 nivôse, an CCXXIII, Philip Langdale a écrit : > There is a long sad story behind all this, but it's somewhat ambiguous as to > whether DVD content should be treated as 720 pixels wide or 704 pixels, with > 16 pixels cut off. If you decide is should be 704 pixels wide, you need to > adjust the sample aspect ratio to keep the final display aspect ratio correct. > > For reasons we are not privy too, nvidia decided that the nvenc encoder should > apply this aspect correction, whether you want it to or not. (I guess there > might be a flag for it, but if there is it's not documented). So, if you want > to transcode DVD content at the original size, you need to adjust the aspect > ratio information you pass to the encoder to compensate for their > 'correction'. > > This 'correction' is only applied to 720x480 and 720x576 content - and it does > so regardless of the input aspect ratio.
Thanks for testing.
> ---
> libavcodec/nvenc.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/libavcodec/nvenc.c b/libavcodec/nvenc.c
> index efa3f04..a51ada2 100644
> --- a/libavcodec/nvenc.c
> +++ b/libavcodec/nvenc.c
> @@ -587,6 +587,13 @@ static av_cold int nvenc_encode_init(AVCodecContext
> *avctx)
> ctx->init_encode_params.darWidth = avctx->width;
> }
>
> + // Compensate for hardware assuming playback will be at 704 pixel width.
Nit: de-compensate for buggy encoders that compensate for...
> + if (avctx->width == 720 &&
> + (avctx->height == 480 || avctx->height == 576)) {
> + ctx->init_encode_params.darWidth *= 44;
> + ctx->init_encode_params.darHeight *= 45;
> + }
Here, and also in Timo's patch, I would advice to use lavu's rational
operators: they will handle overflow better and reduce the result.
> +
> ctx->init_encode_params.frameRateNum = avctx->time_base.den;
> ctx->init_encode_params.frameRateDen = avctx->time_base.num *
> avctx->ticks_per_frame;
Regards,
--
Nicolas George
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