From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3A5E2C3A5A1 for ; Thu, 22 Aug 2019 14:38:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B5D4233FD for ; Thu, 22 Aug 2019 14:38:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731891AbfHVOix (ORCPT ); Thu, 22 Aug 2019 10:38:53 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:34836 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725886AbfHVOix (ORCPT ); Thu, 22 Aug 2019 10:38:53 -0400 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: ezequiel) with ESMTPSA id 8DB5828D11B Message-ID: <5ad0899e81ef8f22545bcb6b01833c493ce2bdc9.camel@collabora.com> Subject: Re: [PATCH v7 02/11] media: uapi: h264: Rename pixel format From: Ezequiel Garcia To: Hans Verkuil , Paul Kocialkowski Cc: linux-media@vger.kernel.org, kernel@collabora.com, Nicolas Dufresne , Tomasz Figa , linux-rockchip@lists.infradead.org, Heiko Stuebner , Jonas Karlman , Philipp Zabel , Boris Brezillon , Alexandre Courbot , fbuergisser@chromium.org, linux-kernel@vger.kernel.org Date: Thu, 22 Aug 2019 11:38:42 -0300 In-Reply-To: <5a6432ce-6d90-9efa-9ae8-400b5ca1d653@xs4all.nl> References: <20190816160132.7352-1-ezequiel@collabora.com> <20190816160132.7352-3-ezequiel@collabora.com> <20190819124110.GB32182@aptenodytes> <20190822115453.GA1627@aptenodytes> <5a6432ce-6d90-9efa-9ae8-400b5ca1d653@xs4all.nl> Organization: Collabora Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5-1.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Thu, 2019-08-22 at 15:47 +0200, Hans Verkuil wrote: > On 8/22/19 1:54 PM, Paul Kocialkowski wrote: > > Hi, > > > > On Mon 19 Aug 19, 17:53, Hans Verkuil wrote: > > > On 8/19/19 2:41 PM, Paul Kocialkowski wrote: > > > > Hi, > > > > > > > > On Fri 16 Aug 19, 13:01, Ezequiel Garcia wrote: > > > > > The V4L2_PIX_FMT_H264_SLICE_RAW name was originally suggested > > > > > because the pixel format would represent H264 slices without any > > > > > start code. > > > > > > > > > > However, as we will now introduce a start code menu control, > > > > > give the pixel format a more meaningful name, while it's > > > > > still early enough to do so. > > > > > > > > I definitely agree that SLICE_RAW is not the suffix we are looking for, but I'm > > > > not sure that _SLICE is self-describing given that we can operate either > > > > per-frame or per-slice, and _SLICE sort of implies the latter. Also, VP8 uses > > > > _FRAME to clearly indicate that it operates per-frame. > > > > > > Well, VP8 doesn't support slices at all. > > > > > > > In addition, the _SLICE suffix is used by MPEG-2 in the stable API. Since we > > > > > > Regarding MPEG-2: while it has a concept of slices, it is my understanding > > > that you never process slices separately, but only full pictures. I may be > > > wrong here. > > > > I don't think that is the case since ffmpeg clearly implements decoding on a > > per-slice basis (mpeg_decode_slice). > > > > Information is also passed on a per-slice basis to VAAPI > > (vaapi_mpeg2_decode_slice) with a distinct data buffer and slice parameter > > buffer for each slice. Among other things, it contains the vertical and > > horizontal positions for the slice, which we can set in the hardware. > > > > > > certainly want MPEG-2 to allow per-slice and per-frame decoding as well as > > > > H.264 and that the _SLICE format is specified to be the broken "concatenated > > > > slices" that cedrus expects, we probably want to use another suffix. This way, > > > > we could deprecated MPEG2_SLICE and introduce a new format for MPEG-2 that would > > > > have consistent naming with the other mpeg formats. > > > > > > I actually think that H264_SLICE is a decent name. > > > > > > I'm less sure about MPEG2_SLICE since I am not sure if it means the same as > > > a H264 slice. > > > > The main problem I see is that we have already specified MPEG2_SLICE in a way > > that is incompatible with the future improvments we want to bring to the API: > > " The output buffer must contain the appropriate number of macroblocks to > > decode a full corresponding frame to the matching capture buffer." > > > > So I only see two possibilities: either we decide to change the specification > > of the pixel format and we can keep using the _SLICE suffix, either we need to > > introduce a new pixel format with another suffix, which should also be reflected > > on other MPEG formats for consistency. Then we can deprecate MPEG2_SLICE and > > have drivers stop using it. > > > > What do you think? > > I'd change the specification of the pixel format. So MPEG2_SLICE now supports > multiple slices if the hardware supports it as well. > > We would need an MPEG2_DECODING_MODE control as well, that currently would > read FRAME based only. > That's exactly what I was about to suggest. Regards, Ezequiel