Re: [FFmpeg-devel] [PATCH] avformat/hlsenc: Use HLS version 2 if rounded durations are enabled

[<lucy@absolucy.moe>]

Yes. Version 3 is just Version 2 with floating point durations.

-----Original Message-----
From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of Steven Liu
Sent: Sunday, June 26, 2022 10:17 PM
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] avformat/hlsenc: Use HLS version 2 if rounded durations are enabled

Lucy <lucy@absolucy.moe> 于2022年6月27日周一 09:12写道：
>
> This allows for wider compatibility with older devices, such as those 
> running iOS 3. The only difference between HLS version 2 and version 3 
> is that version 3 supports non-integer EXTINF values, and as such, we 
> can default to version 2 if we're using whole-integer EXTINFs anyways, 
> when `-hls_flags round_durations` is set.
>
> As this code seems to otherwise consistently use the lowest compatible 
> version, this seems to fit in properly with existing behavior.
>
> Testing confirms with that this patch, HLS output can work all the way 
> back to iOS 3.
>
> This is my first contribution to ffmpeg, so please tell me if I did 
> anything wrong, and I'll try my best to fix it.
>
> Signed-off-by: Lucy <lucy@absolucy.moe>
> ---
>  doc/muxers.texi      | 2 ++
>  libavformat/hlsenc.c | 6 +++++-
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/doc/muxers.texi b/doc/muxers.texi index 
> b6cafaa5fd..b2f4326aae 100644
> --- a/doc/muxers.texi
> +++ b/doc/muxers.texi
> @@ -1060,6 +1060,8 @@ and remove the @code{#EXT-X-ENDLIST} from the 
> old segment list.
>  @item round_durations
>  Round the duration info in the playlist file segment info to integer  
> values, instead of using floating point.
> +If there are no other features requiring higher HLS versions be used, 
> +then this will allow ffmpeg to output a HLS version 2 m3u8.
>
>  @item discont_start
>  Add the @code{#EXT-X-DISCONTINUITY} tag to the playlist, before the 
> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c index 
> 3bafddfa61..7c097b4bf2 100644
> --- a/libavformat/hlsenc.c
> +++ b/libavformat/hlsenc.c
> @@ -1550,7 +1550,11 @@ static int hls_window(AVFormatContext *s, int 
> last, VariantStream *vs)
>      double *prog_date_time_p = (hls->flags & HLS_PROGRAM_DATE_TIME) ?
> &prog_date_time : NULL;
>      int byterange_mode = (hls->flags & HLS_SINGLE_FILE) || 
> (hls->max_seg_size > 0);
>
> -    hls->version = 3;
> +    hls->version = 2;
Do you mean the functions which support from version 3 but not use HLS_ROUND_DURATIONS should use version 2?
> +    if (!(hls->flags & HLS_ROUND_DURATIONS)) {
> +        hls->version = 3;
> +    }
> +
>      if (byterange_mode) {
>          hls->version = 4;
>          sequence = 0;
> --
> 2.36.1
>
>
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Thanks
Steven
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