From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Garlick Subject: Re: Video narration Date: Mon, 06 May 2019 21:34:40 +0100 Message-ID: <4e37c425257247b33a7559c92fbf2c063c334e45.camel@tourbillion-technology.com> References: <0b31a2364a97f26bbea1fed9e3390a2a526d6c77.camel@tourbillion-technology.com> <30bca313b07d1dc65c73d2e2c4d0e8907144081d.camel@tourbillion-technology.com> <4945ad6d7434cba7dc65e33ef97a4185a4e4a266.camel@tourbillion-technology.com> <59ab26112bb25301e6382e469734d11227c3ff06.camel@tourbillion-technology.com> <131ffa7aacc4db6acbd3e35f84079326096ac35c.camel@tourbillion-technology.com> <99cb429102f8ae64ad711edeb3c1f5256204e4bc.camel@tourbillion-technology.com> <87v9ynpuwx.fsf@elephly.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from eggs.gnu.org ([209.51.188.92]:53270) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hNkJz-0005YW-1t for guix-devel@gnu.org; Mon, 06 May 2019 16:34:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hNkJw-0004dl-Rb for guix-devel@gnu.org; Mon, 06 May 2019 16:34:45 -0400 In-Reply-To: <87v9ynpuwx.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 Hi Ricardo, > Are you saying you want to take snapshots in larger intervals and pad > the intermediate frames with duplicates of previous frames? Thank you for writing the snap! procedure. It is writing the output as intended. The problem we ran into was to do with the timing. If you go back in this thread you will see the history. In order to produce .webm files that are compatible with the Firefox browser it is necessary to eliminate gaps in the audio streams. ffmpeg can do this automatically using the 'apad' filter. However, it will truncate the audio stream if the video stream is shorter in duration than the audio stream. So, in preparing the cli session files we need to be able to accurately set the duration of the last 'sleep' command. Since we know the frame rate (25 fps) it is straightforward to calculate the number of repeated frames we need for any given duration. This is the job of the new 'repeat' procedure. In this way we effectively replace the timer with a counter. The session files now need to be checked to tune the sleep commands to synchronize with the audio stream. I will be able to look at 02-daily- use1 again tomorrow. Best regards, Paul.