[FFmpeg-devel] [PATCH] libavcodec: fix field_order labelling

[Marton Balint]

On Sat, 12 Aug 2017, Dave Rice wrote:

[..]

> Also utils.c associates these field order values with the following labels:
>
>> AV_FIELD_TB  -> "top coded first (swapped)";
>> AV_FIELD_BT -> "bottom coded first (swapped)";
>
> From my reading, I infer that "top coded first (swapped)” means "top 
> coded first, bottom displayed first”; however in practice from files 
> generated by QuickTime and FFmpeg files with a value of TB have the top 
> field displayed first, so I think the labels are swapped. In the patch 
> below I suggest using “top first (interleaved)” for TB and “bottom first 
> (interleaved)” for BT.
>
> Comments?
>
>
> From de871b3fa891fa0ae6856461c1f8305cc889cde7 Mon Sep 17 00:00:00 2001
> From: Dave Rice <dave at dericed.com>
> Date: Sat, 12 Aug 2017 12:30:43 -0400
> Subject: [PATCH] libavcodec: fix field_order labelling
>
> ---
> libavcodec/avcodec.h | 4 ++--
> libavcodec/utils.c   | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
> index c594993766..37c39072b3 100644
> --- a/libavcodec/avcodec.h
> +++ b/libavcodec/avcodec.h
> @@ -1726,8 +1726,8 @@ enum AVFieldOrder {
>     AV_FIELD_PROGRESSIVE,
>     AV_FIELD_TT,          //< Top coded_first, top displayed first
>     AV_FIELD_BB,          //< Bottom coded first, bottom displayed first
> -    AV_FIELD_TB,          //< Top coded first, bottom displayed first
> -    AV_FIELD_BT,          //< Bottom coded first, top displayed first
> +    AV_FIELD_TB,          //< Interleaved coding, top displayed first
> +    AV_FIELD_BT,          //< Interleaved coding, bottom displayed first
> };

I agree that a lot of stuff in the codebase is consistent with the updated 
descriptions. However, as far as I see libavformat/mxfdec.c seems to 
follow the existing docs, so I think that needs changing as well.

Regards,
Marton