[FFmpeg-devel] [PATCH] movenc: write clap tag

[Dave Rice]

> On Jul 9, 2017, at 7:26 PM, Dave Rice <dave at dericed.com> wrote:
> 
> 
>> On Jul 7, 2017, at 7:06 PM, Derek Buitenhuis <derek.buitenhuis at gmail.com> wrote:
>> 
>> On 7/7/2017 10:13 PM, James Almer wrote:
>>> Isn't this necessary only for files with raw video? As is, this box
>>> would be written on any mov file with a video stream.
>> 
>> This was addressed a previous email:
>> 
>>   http://lists.ffmpeg.org/pipermail/ffmpeg-devel/2017-July/213350.html
>> 
>> I guess the spec is up for interpretation.
> 
> The quicktime spec says "This is a mandatory extension for all uncompressed Y´CbCr data formats”. It doesn’t clarify if the clap atom is recommended or not in mov files that are not “uncompressed Y´CbCr”, though it would make sense if the video container needs to store cropping data. I think constraining the change for only  “uncompressed Y´CbCr” would be more cautious though. I’ll revise my patch to include the condition and resubmit.
> 
> If the patch only impacts “uncompressed Y´CbCr” would any fate updates be needed?
> Dave Rice

Here’s an update to only write the clap atom for the specific uncompressed encodings listed in TN2162.

From 37457c1ee135f39452b91b047af4adf1ec43464b Mon Sep 17 00:00:00 2001
From: Dave Rice <dave at dericed.com>
Date: Thu, 16 Nov 2017 11:29:06 -0500
Subject: [PATCH] avformat/movenc: write clap atom for uncompressed yuv in mov

fixes 6145
---
 libavformat/movenc.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index cc3fc19d9b..18232e8ba3 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -1686,6 +1686,21 @@ static int mov_write_sv3d_tag(AVFormatContext *s, AVIOContext *pb, AVSphericalMa
     return update_size(pb, sv3d_pos);
 }
 
+static int mov_write_clap_tag(AVIOContext *pb, MOVTrack *track)
+{
+    avio_wb32(pb, 40);
+    ffio_wfourcc(pb, "clap");
+    avio_wb32(pb, track->par->width); /* apertureWidth_N */
+    avio_wb32(pb, 1); /* apertureWidth_D (= 1) */
+    avio_wb32(pb, track->height); /* apertureHeight_N */
+    avio_wb32(pb, 1); /* apertureHeight_D (= 1) */
+    avio_wb32(pb, 0); /* horizOff_N (= 0) */
+    avio_wb32(pb, 1); /* horizOff_D (= 1) */
+    avio_wb32(pb, 0); /* vertOff_N (= 0) */
+    avio_wb32(pb, 1); /* vertOff_D (= 1) */
+    return 40;
+}
+
 static int mov_write_pasp_tag(AVIOContext *pb, MOVTrack *track)
 {
     AVRational sar;
@@ -1970,6 +1985,16 @@ static int mov_write_video_tag(AVIOContext *pb, MOVMuxContext *mov, MOVTrack *tr
         mov_write_pasp_tag(pb, track);
     }
 
+    int uncompressed_ycbcr = ((track->par->codec_id == AV_CODEC_ID_RAWVIDEO && track->par->format == AV_PIX_FMT_UYVY422)
+                           || (track->par->codec_id == AV_CODEC_ID_RAWVIDEO && track->par->format == AV_PIX_FMT_YUYV422)
+                           ||  track->par->codec_id == AV_CODEC_ID_V308
+                           ||  track->par->codec_id == AV_CODEC_ID_V408
+                           ||  track->par->codec_id == AV_CODEC_ID_V410
+                           ||  track->par->codec_id == AV_CODEC_ID_V210);          
+    if (uncompressed_ycbcr){
+        mov_write_clap_tag(pb, track);
+    }
+
     if (mov->encryption_scheme != MOV_ENC_NONE) {
         ff_mov_cenc_write_sinf_tag(track, pb, mov->encryption_kid);
     }
-- 
2.15.0