From patchwork Mon Sep 12 22:28:24 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jonathan Campbell X-Patchwork-Id: 556 Delivered-To: ffmpegpatchwork@gmail.com Received: by 10.103.140.134 with SMTP id o128csp1847947vsd; Mon, 12 Sep 2016 15:29:43 -0700 (PDT) X-Received: by 10.194.92.2 with SMTP id ci2mr16342433wjb.58.1473719383244; Mon, 12 Sep 2016 15:29:43 -0700 (PDT) Return-Path: Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org. [79.124.17.100]) by mx.google.com with ESMTP id p13si17462473wmd.97.2016.09.12.15.29.38; Mon, 12 Sep 2016 15:29:43 -0700 (PDT) Received-SPF: pass (google.com: domain of ffmpeg-devel-bounces@ffmpeg.org designates 79.124.17.100 as permitted sender) client-ip=79.124.17.100; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ffmpeg-devel-bounces@ffmpeg.org designates 79.124.17.100 as permitted sender) smtp.mailfrom=ffmpeg-devel-bounces@ffmpeg.org Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id 27AE7689F13; Tue, 13 Sep 2016 01:29:24 +0300 (EEST) X-Original-To: ffmpeg-devel@ffmpeg.org Delivered-To: ffmpeg-devel@ffmpeg.org Received: from p3plsmtps2ded04.prod.phx3.secureserver.net (p3plsmtps2ded04.prod.phx3.secureserver.net [208.109.80.198]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id AFD7D689AE1 for ; Tue, 13 Sep 2016 01:29:16 +0300 (EEST) Received: from ip-192-169-235-64.secureserver.net ([192.169.235.64]) by : HOSTING RELAY : with SMTP id jZiDbAEkL1EcLjZiDbm3uK; Mon, 12 Sep 2016 15:28:25 -0700 x-originating-ip: 192.169.235.64 Received: from 50-245-141-73-static.hfc.comcastbusiness.net ([50.245.141.73]:47576 helo=[172.19.234.190]) by ip-192-169-235-64.secureserver.net with esmtpsa (TLSv1:DHE-RSA-CAMELLIA256-SHA:256) (Exim 4.82) (envelope-from ) id 1bjZiD-0003Dx-KJ for ffmpeg-devel@ffmpeg.org; Mon, 12 Sep 2016 15:28:25 -0700 Message-ID: <57D72C08.4020808@impactstudiopro.com> Date: Mon, 12 Sep 2016 15:28:24 -0700 From: Jonathan Campbell User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: FFmpeg development discussions and patches X-CMAE-Envelope: MS4wfFS+DWyHqoKXhE6ErlMniblA1vuv537ZFS8C5zxM0vPLs6/5OPiq8vLDsaqVbnxpQZxm14uha/+1NhOKOzPAYuXWw4JQ+SlwA8I1U1pVRWVag6drJaUS +GPu5tebCKoAWdY6B/UQeaidGQ4VQegDP9kgTHoQKKmuwPOnhA41/DVajN61oVO3Da8dZNvbFB9xfxPQ7DN1uj3JfD7ljWHRxd042cZLuqYJvwME+D5V+yL6 Subject: [FFmpeg-devel] mpeg12dec fix up DVD caption handling X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.20 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 Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" These patches fix up the DVD caption handling in mpeg12dec.c to better handle odd cases. It's based on code I've written elsewhere to handle captions. While it's common for these packets to contain 15 frames worth and start on the odd field there are also DVDs that start on even field or even encode extra fields and switch starting fields. Part of the patch is to document comprehensively the format of the DVD caption packet. Jonathan Campbell From 9213012c7d8ceef2af43fe3c218b1b50728e8f80 Mon Sep 17 00:00:00 2001 From: Jonathan Campbell Date: Mon, 12 Sep 2016 12:34:48 -0700 Subject: [PATCH 1/2] add comments documenting the format of the DVD CC user-data packet. this is to aid development and maintenance of that code. --- libavcodec/mpeg12dec.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c index 204a578..522621a 100644 --- a/libavcodec/mpeg12dec.c +++ b/libavcodec/mpeg12dec.c @@ -2262,7 +2262,32 @@ static int mpeg_decode_a53_cc(AVCodecContext *avctx, return 1; } else if (buf_size >= 11 && p[0] == 'C' && p[1] == 'C' && p[2] == 0x01 && p[3] == 0xf8) { - /* extract DVD CC data */ + /* extract DVD CC data + * for more information see: [https://en.wikipedia.org/wiki/EIA-608#DVD_GOP_User_Data_Insertion] + * + * uint32_t user_data_start_code 0x000001B2 (big endian) + * uint16_t user_identifier 0x4343 "CC" + * uint8_t user_data_type_code 0x01 + * uint8_t caption_block_size 0xF8 + * uint8_t + * bit 7 caption_odd_field_first 1=odd field (CC1/CC2) first 0=even field (CC3/CC4) first + * bit 6 caption_filler 0 + * bit 5:1 caption_block_count number of caption blocks (pairs of caption words = frames). Most DVDs use 15 per start of GOP. + * bit 0 caption_extra_field_added 1=one additional caption word + * + * struct caption_field_block { + * uint8_t + * bit 7:1 caption_filler 0x7F (all 1s) + * bit 0 caption_field_odd 1=odd field (this is CC1/CC2) 0=even field (this is CC3/CC4) + * uint8_t caption_first_byte + * uint8_t caption_second_byte + * } caption_block[(caption_block_count * 2) + caption_extra_field_added]; + * + * Some DVDs encode caption data for both fields with caption_field_odd=1. The only way to decode the fields + * correctly is to start on the field indicated by caption_odd_field_first and count between odd/even fields. + * Don't assume that the first caption word is the odd field. There do exist MPEG files in the wild that start + * on the even field. There also exist DVDs in the wild that encode an odd field count and the + * caption_extra_field_added/caption_odd_field_first bits change per packet to allow that. */ int cc_count = 0; int i; // There is a caption count field in the data, but it is often