From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?Q?G=C3=A1bor_Boskovits?= Subject: Re: Video subtitles Date: Thu, 20 Dec 2018 22:08:45 +0100 Message-ID: References: <87pntwsjmz.fsf@elephly.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Return-path: Received: from eggs.gnu.org ([2001:4830:134:3::10]:43636) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ga5Yz-0001wp-VQ for guix-devel@gnu.org; Thu, 20 Dec 2018 16:09:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ga5Yz-0007nP-6D for guix-devel@gnu.org; Thu, 20 Dec 2018 16:09:02 -0500 Received: from mail-it1-x12d.google.com ([2607:f8b0:4864:20::12d]:51098) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1ga5Yz-0007mH-0u for guix-devel@gnu.org; Thu, 20 Dec 2018 16:09:01 -0500 Received: by mail-it1-x12d.google.com with SMTP id z7so4084468iti.0 for ; Thu, 20 Dec 2018 13:08:59 -0800 (PST) In-Reply-To: <87pntwsjmz.fsf@elephly.net> List-Id: "Development of GNU Guix and the GNU System distribution." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org Sender: "Guix-devel" To: Ricardo Wurmus Cc: Guix-devel Hello, Ricardo Wurmus ezt =C3=ADrta (id=C5=91pont: 2018. dec.= 20., Cs, 9:26): > > > Hi Laura, > > > The first question I need to answer is if subtitles are going to be > > present all the time as part of the video, or they should be able to > > be disabled. We had that discussion somewhere, but if they are going > > to be present as part of the video (hardsubs) only .srt and .ass - the > > ones created by default by aegisub - are supported by ffmpeg: > > https://trac.ffmpeg.org/wiki/HowToBurnSubtitlesIntoVideo > > The subtitles should be provided as a separate file, so that they can > easily be swapped out or disabled. Some container formats allow > embedding the subtitles, but we would need to embed all subtitles in all > language variants of all video files, and this seems like more work. > Having the subtitles as separate files is more convenient for > processing. > Yes, and the embeding into the container can be automated at the end if nee= ded. > > I remembered how much time each audio file lasted, so I added one > > subtitle for each svg file that appears in the video - they were just > > three- with the full content of what is said in the audio. > > It is more common to have a single subtitle file per video. It would be ok to have a single subtitle file. > > > The drawback of this is that each svg file in the video has the full > > subtitle text before the speaker mentions those words - I will ask > > Bj=C3=B6rn tomorrow to upload it to their IPFS so that you can see what= I > > mean. > > You can time the appearance of text. I=E2=80=99ve only ever written srt > subtitle files by hand before, but they are all similar in that they > associate a piece of text with a timestamp. The text is then displayed > at the specified time only. > > You can figure out the appropriate timestamps by playing back the video > and recording the times when something is said that should be titled. > So to make this more explicit, you could break down the text to smaller chunks, then time the appearance of those. > > When choosing the format of the subtitles, Ricardo mentioned that it > > was better using usf because it had support for styling. The good news > > is that aegisub allows us to do so in their own interface, but in > > their .ass format, one of the two that supports ffmpeg, which is not > > compatible, I guess, with the formats mentioned in po4a for > > translation. However the .ass subtitle can be exported as .ttxt - > > which is an XML, and that can be converted back to .ass. > > =E2=80=9C.ass=E2=80=9D files are very popular and very rich in styling fe= atures. =E2=80=9C.usf=E2=80=9D > files are less commonly seen in the wild. > > I have no strong opinions about using =E2=80=9C.usf=E2=80=9D. =E2=80=9C.= ass=E2=80=9D may just be fine. > Apparently, it can be converted to po files for translation with > =E2=80=9Csub2po=E2=80=9D, which is part of the =E2=80=9Ctranslate=E2=80= =9D toolkit. I have no > experience with this, and I think it would be better to use a format > that didn=E2=80=99t require even more tools to work with. > > This shouldn=E2=80=99t block you, though. It is fine to use Aegisub manu= ally to > create the initial subtitle and then convert it to another format. > Aegisub does not need to be part of the automated process to compile the > videos. > > -- > Ricardo > > I believe that we don't want to do anything fancy with the subtitles, so I guess any format would be just fine, provided we have tool support. Best regards, g_bor