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 3B32645795 for ; Tue, 21 Feb 2023 09:41:50 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id C509668C08D; Tue, 21 Feb 2023 11:41:47 +0200 (EET) Received: from mail.frobbit.se (mail.frobbit.se [85.30.129.176]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 6E2B868BF93 for ; Tue, 21 Feb 2023 11:41:41 +0200 (EET) Received: from [10.10.150.173] (1346516434.ip.84grams.net [134.65.164.34]) by mail.frobbit.se (Postfix) with ESMTPSA id CDFA724C9A for ; Tue, 21 Feb 2023 10:41:40 +0100 (CET) Message-ID: From: Tomas =?ISO-8859-1?Q?H=E4rdin?= To: FFmpeg development discussions and patches Date: Tue, 21 Feb 2023 10:41:40 +0100 In-Reply-To: References: <20230213180936.815-1-nicolas.gaullier@cji.paris> <20230213180936.815-4-nicolas.gaullier@cji.paris> User-Agent: Evolution 3.38.3-1+deb11u1 MIME-Version: 1.0 Subject: Re: [FFmpeg-devel] [PATCH 3/6] avformat/s337m: New ff_s337m_probe() 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: fre 2023-02-17 klockan 10:12 +0000 skrev Nicolas Gaullier: > > The logic here is a bit hairy and I don't have time atm to digest > > it, but is it entirely contained in S337m or would one need to read > > other specs too? > > > > /Tomas > > ff_s337m_probe is very similar to s337m_probe: what mainly differs is > the input parameters. > The one little thing I added is the S337M_PROBE_GUARDBAND_MIN_BYTES. > Currently it is set to 0, so has no effect (and of course I can > remove it if someone object). > There is two things to know about it: > - one is that some DolbyE decoder implementations does not support > the s337m sync word to be the first word, > A minimal guard band (full of zero) is required in such a case : 1 > word is enough in the cases I experimented. > One developer might find it useful to set > S337M_PROBE_GUARDBAND_MIN_BYTES to 1 in order to ffprobe-qc/reject > such files. > - one other thing is that, currently, the detection is based on 3 > consecutive samples, > But there are other implementations in the wild. A common single- > sample implementation is to simply require > a sufficient S337M_PROBE_GUARDBAND_MIN_BYTES in order to avoid a fake > detection. > (for 16 bits, this is really dangerous!; for 24 bits, I think it is > fair but would still require some little additions to be 100% sure). What a mess.. And there's no other way to reliably probe this? /Tomas _______________________________________________ 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".