[FFmpeg-devel] movenc: add write_btrt option

["zhilizhao(赵志立)"]

> On Apr 3, 2022, at 1:07 PM, Eran Kornblau <eran.kornblau at kaltura.com> wrote:
> 
> Trying my luck in a new thread…
> 
> This patch is in continuation to this discussion –
> https://ffmpeg.org/pipermail/ffmpeg-devel/2022-March/294623.html
> 
> supports forcing or disabling the writing of the btrt atom.
> the default behavior is to write the atom only for mp4 mode.
> ---
>  libavformat/movenc.c | 30 +++++++++++++++++++-----------
>  libavformat/movenc.h |  1 +
>  2 files changed, 20 insertions(+), 11 deletions(-)
> 
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index 4c868919ae..b75f1c6909 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> 
[…]
>  
> -    if (track->mode == MODE_MP4 &&
> -            ((ret = mov_write_btrt_tag(pb, track)) < 0))
> -        return ret;
> +    if ((mov->write_btrt == -1 && track->mode == MODE_MP4) || mov->write_btrt == 1) {
> +        if ((ret = mov_write_btrt_tag(pb, track)) < 0) {
> +            return ret;
> +        }
> +    }

I prefer to handle the auto mode (mov->write_btrt == -1) in a single place,
so we don’t need to change multiple lines if the condition changed, e.g.,
enable btrt for MODE_MOV. Please correct me if I’m wrong, mov_init() has all
of the contexts to overwrite mov->write_btrt.