[FFmpeg-devel] [PATCH v2 5/5] vf_ccrepack: Add new filter to repack CEA-708 side data

[Devin Heitmueller]

THis filter can correct certain issues seen from upstream sources
where the cc_count is not properly set or the CEA-608 tuples are
not at the start of the payload as expected.

Make use of the ccfifo to extract and immediately repack the CEA-708
side data, thereby removing any extra padding and ensuring the 608
tuples are at the front of the payload.

Signed-off-by: Devin Heitmueller <dheitmueller at ltnglobal.com>
---
 doc/filters.texi          |  10 +++++
 libavfilter/Makefile      |   1 +
 libavfilter/allfilters.c  |   1 +
 libavfilter/vf_ccrepack.c | 100 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 112 insertions(+)
 create mode 100644 libavfilter/vf_ccrepack.c

diff --git a/doc/filters.texi b/doc/filters.texi
index 120fe66..e72e73d 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -8930,6 +8930,16 @@ Only deinterlace frames marked as interlaced.
 The default value is @code{all}.
 @end table
 
+ at section ccrepack
+
+Repack CEA-708 closed captioning side data
+
+This filter fixes various issues seen with commerical encoders
+related to upstream malformed CEA-708 payloads, specifically
+incorrect number of tuples (wrong cc_count for the target FPS),
+and incorrect ordering of tuples (i.e. the CEA-608 tuples are not at
+the first entries in the payload).
+
 @section cas
 
 Apply Contrast Adaptive Sharpen filter to video stream.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 628ade8..3d0b3ad 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -212,6 +212,7 @@ OBJS-$(CONFIG_BOXBLUR_OPENCL_FILTER)         += vf_avgblur_opencl.o opencl.o \
                                                 opencl/avgblur.o boxblur.o
 OBJS-$(CONFIG_BWDIF_FILTER)                  += vf_bwdif.o yadif_common.o
 OBJS-$(CONFIG_CAS_FILTER)                    += vf_cas.o
+OBJS-$(CONFIG_CCREPACK_FILTER)               += vf_ccrepack.o
 OBJS-$(CONFIG_CHROMABER_VULKAN_FILTER)       += vf_chromaber_vulkan.o vulkan.o vulkan_filter.o
 OBJS-$(CONFIG_CHROMAHOLD_FILTER)             += vf_chromakey.o
 OBJS-$(CONFIG_CHROMAKEY_FILTER)              += vf_chromakey.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index d7db46c..b38550b 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -196,6 +196,7 @@ extern const AVFilter ff_vf_boxblur;
 extern const AVFilter ff_vf_boxblur_opencl;
 extern const AVFilter ff_vf_bwdif;
 extern const AVFilter ff_vf_cas;
+extern const AVFilter ff_vf_ccrepack;
 extern const AVFilter ff_vf_chromaber_vulkan;
 extern const AVFilter ff_vf_chromahold;
 extern const AVFilter ff_vf_chromakey;
diff --git a/libavfilter/vf_ccrepack.c b/libavfilter/vf_ccrepack.c
new file mode 100644
index 0000000..063c360
--- /dev/null
+++ b/libavfilter/vf_ccrepack.c
@@ -0,0 +1,100 @@
+/*
+ * CEA-708 Closed Caption Repacker
+ * Copyright (c) 2023 LTN Global Communications
+ *
+ * Author: Devin Heitmueller <dheitmueller at ltnglobal.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/*
+ * Repackage CEA-708 arrays, which deals with incorrect cc_count for a given
+ * output framerate, and incorrect 708 padding.
+ *
+ * See CEA CEA-10-A "EIA-708-B Implementation Guidance", Section 26.5
+ * "Grouping DTVCC Data Within user_data() Structure"
+ */
+
+#include "avfilter.h"
+#include "internal.h"
+#include "ccfifo.h"
+#include "libavutil/opt.h"
+
+typedef struct CCRepackContext
+{
+    const AVClass *class;
+    AVCCFifo *cc_fifo;
+} CCRepackContext;
+
+static const AVOption ccrepack_options[] = {
+    {  NULL }
+};
+
+AVFILTER_DEFINE_CLASS(ccrepack);
+
+static int config_input(AVFilterLink *link)
+{
+    CCRepackContext *ctx = link->dst->priv;
+
+    if (!(ctx->cc_fifo = av_ccfifo_alloc(&link->frame_rate, ctx)))
+        av_log(ctx, AV_LOG_VERBOSE, "Failure to setup CC FIFO queue.  Captions will be passed through\n");
+
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
+{
+    CCRepackContext *ctx = inlink->dst->priv;
+    AVFilterLink *outlink = inlink->dst->outputs[0];
+
+    av_ccfifo_extract(ctx->cc_fifo, frame);
+    av_ccfifo_inject(ctx->cc_fifo, frame);
+
+    return ff_filter_frame(outlink, frame);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    CCRepackContext *s = ctx->priv;
+    av_ccfifo_freep(&s->cc_fifo);
+}
+
+static const AVFilterPad avfilter_vf_ccrepack_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+	.config_props = config_input,
+    },
+};
+
+static const AVFilterPad avfilter_vf_ccrepack_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+};
+
+AVFilter ff_vf_ccrepack = {
+    .name        = "ccrepack",
+    .description = NULL_IF_CONFIG_SMALL("Repack CEA-708 closed caption metadata"),
+    .uninit      = uninit,
+    .priv_size   = sizeof(CCRepackContext),
+    .priv_class  = &ccrepack_class,
+    FILTER_INPUTS(avfilter_vf_ccrepack_inputs),
+    FILTER_OUTPUTS(avfilter_vf_ccrepack_outputs),
+};
-- 
1.8.3.1