From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by master.gitmailbox.com (Postfix) with ESMTP id 0299E45F28 for ; Wed, 19 Apr 2023 15:06:29 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id 1ACF768BF42; Wed, 19 Apr 2023 18:06:27 +0300 (EEST) Received: from w4.tutanota.de (w4.tutanota.de [81.3.6.165]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 18C4768BF33 for ; Wed, 19 Apr 2023 18:06:20 +0300 (EEST) Received: from tutadb.w10.tutanota.de (unknown [192.168.1.10]) by w4.tutanota.de (Postfix) with ESMTP id C47C1106015D for ; Wed, 19 Apr 2023 15:06:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1681916779; s=s1; d=lynne.ee; h=From:From:To:To:Subject:Subject:Content-Description:Content-ID:Content-Type:Content-Type:Content-Transfer-Encoding:Content-Transfer-Encoding:Cc:Date:Date:In-Reply-To:In-Reply-To:MIME-Version:MIME-Version:Message-ID:Message-ID:Reply-To:References:References:Sender; bh=pmcuan0T4HW91W0eyjRshEjBcMRhvVuK+58Bt9giCXc=; b=JAznHBKqrw6F2JeXIzVgaXsiae2LeDfR6dyMfRWyVwT8UdMswZBC7pAPDSfW70+F GAISuyFmTsjD3oMRuIz+cjFs+nEZnZJaqySC4nSpZy9aB+//XCIqW9LyzWrnlqDhvaG RX/5Fql2oW2ukyLWwsvlyYmXNJWVaw0IG7qMILHqAmQ3ctgGHFpH1UF5Uu3oOnxUwuL ajC6aMaqWqLU8d9Y5WyCbxf3MqmGjrDejrz8TAdRyBcj6UALXdBK7vBX8ccv9VHMdnG WmwomikdbOh+GUTM7CU5piZWRJ9Zla7QovS5HX+toXBYo3kuu5UbjY6JXSNbA4Oi6bk JQJtC25GxA== Date: Wed, 19 Apr 2023 17:06:19 +0200 (CEST) From: Lynne To: FFmpeg development discussions and patches Message-ID: In-Reply-To: <0ff1089c-a964-21a8-a8f9-0f7c39ba63f9@gmail.com> References: <20230417143930.1186-1-jamrial@gmail.com> <0ff1089c-a964-21a8-a8f9-0f7c39ba63f9@gmail.com> MIME-Version: 1.0 Subject: Re: [FFmpeg-devel] [PATCH] avutil/frame: use bitfields for some boolean and enum fields X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: Apr 17, 2023, 19:27 by jamrial@gmail.com: > On 4/17/2023 2:25 PM, Lynne wrote: > >> Apr 17, 2023, 17:15 by jamrial@gmail.com: >> >>> On 4/17/2023 12:00 PM, Lynne wrote: >>> >>>> Apr 17, 2023, 16:40 by jamrial@gmail.com: >>>> >>>>> Should reduce the size of AVFrame in the next major bump without changing the API. >>>>> >>>>> Suggested-by: Anton Khirnov >>>>> Signed-off-by: James Almer >>>>> --- >>>>> This supersedes "avutil/frame: add new interlaced and top_field_first flags" >>>>> and "avutil/frame: add a keyframe flag to AVFrame". >>>>> >>>>> libavutil/frame.h | 56 +++++++++++++++++++++++++++++++++++++++++++++ >>>>> libavutil/version.h | 1 + >>>>> 2 files changed, 57 insertions(+) >>>>> >>>>> diff --git a/libavutil/frame.h b/libavutil/frame.h >>>>> index f85d630c5c..c26067f383 100644 >>>>> --- a/libavutil/frame.h >>>>> +++ b/libavutil/frame.h >>>>> @@ -416,6 +416,7 @@ typedef struct AVFrame { >>>>> */ >>>>> int format; >>>>> +#if FF_API_BITFIELDS >>>>> /** >>>>> * 1 -> keyframe, 0-> not >>>>> */ >>>>> @@ -425,6 +426,57 @@ typedef struct AVFrame { >>>>> * Picture type of the frame. >>>>> */ >>>>> enum AVPictureType pict_type; >>>>> +#else >>>>> + /** >>>>> + * 1 -> keyframe, 0-> not >>>>> + */ >>>>> + unsigned int key_frame: 1; >>>>> + >>>>> + /** >>>>> + * The content of the picture is interlaced. >>>>> + */ >>>>> + unsigned int interlaced_frame: 1; >>>>> + >>>>> + /** >>>>> + * If the content is interlaced, is top field displayed first. >>>>> + */ >>>>> + unsigned int top_field_first: 1; >>>>> + >>>>> + /** >>>>> + * Tell user application that palette has changed from previous frame. >>>>> + */ >>>>> + unsigned int palette_has_changed: 1; >>>>> + >>>>> + /** >>>>> + * Reserved. Must not be touched. >>>>> + */ >>>>> + unsigned int reserved_bitfield: (sizeof(unsigned int) * 8) - 9; >>>>> + >>>>> + /** >>>>> + * MPEG vs JPEG YUV range. >>>>> + * - encoding: Set by user >>>>> + * - decoding: Set by libavcodec >>>>> + */ >>>>> + enum AVColorRange color_range: 2; >>>>> + >>>>> + enum AVChromaLocation chroma_location: 3; >>>>> >>>> >>>> Definitely disagree on all non-8bit field limits. >>>> The reserved_bitfield is especially ugly. >>>> A few wasted bits wouldn't affect much, we don't even support building on 6502s. >>>> Use bools, or limit them to 8bits so we can use bools when we bump? >>>> The rest can be limited to 8bits. >>>> >>> >>> I added reserved_bitfield to turn what otherwise will be compiler-injected padding into something that can be reused if we were to add new fields here instead of at the end of the struct. I can remove it if you prefer, and make color_range and chroma_location into :8. >>> Like i told you on IRC, i want to keep these as enum and not change their type to uint8_t, _Bool, or anything like that. Also, i wouldn't be surprised if using _Bool breaks some old weird compilers. >>> >>> With this change, I'm replacing 40 bytes worth of fields with 8 bytes worth of fields with no API break. >>> >> >> I'm fine with enums staying as enums, and limiting them to 8 bits. >> I'm not fine with limiting flags to 1 bit or 2/3 bits. I'd like for them to >> be limited to 8 bits, and changing their type to bool or uint8_t at the >> bump. You're still saving at least 21 bytes. >> > > But why use 8 bits when we can use 1? > No need for explicit padding. They're able to be set via pointers, simplifying FFI. They're faster to access. We could need to extend color_range and chroma_location in the future. It's not worth saving a few tens of bits in a large struct that's going to have to grow larger if we want to support e.g. subtitles in avframes. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".