lavc: add a bitstream filter for splitting VP9 superframes

Partially based on code by Ronald S. Bultje <rsbultje@gmail.com>.

doc/bitstream_filters.texi

@@ -95,4 +95,8 @@ This bitstream filter passes the packets through unchanged.
 
 @section remove_extradata
 
+@section vp9_superframe_split
+
+Split VP9 superframes into single frames.
+
 @c man end BITSTREAM FILTERS

libavcodec/Makefile

@@ -767,6 +767,7 @@ OBJS-$(CONFIG_NOISE_BSF)                  += noise_bsf.o
 OBJS-$(CONFIG_NULL_BSF)                   += null_bsf.o
 OBJS-$(CONFIG_REMOVE_EXTRADATA_BSF)       += remove_extradata_bsf.o
 OBJS-$(CONFIG_TEXT2MOVSUB_BSF)            += movsub_bsf.o
+OBJS-$(CONFIG_VP9_SUPERFRAME_SPLIT_BSF)   += vp9_superframe_split_bsf.o
 
 # thread libraries
 OBJS-$(HAVE_LIBC_MSVCRT)               += file_open.o

libavcodec/bitstream_filters.c

@@ -38,6 +38,7 @@ extern const AVBitStreamFilter ff_null_bsf;
 extern const AVBitStreamFilter ff_text2movsub_bsf;
 extern const AVBitStreamFilter ff_noise_bsf;
 extern const AVBitStreamFilter ff_remove_extradata_bsf;
+extern const AVBitStreamFilter ff_vp9_superframe_split_bsf;
 
 #include "libavcodec/bsf_list.c"
 

libavcodec/vp9_superframe_split_bsf.c

@@ -0,0 +1,146 @@
+/*
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * This bitstream filter splits VP9 superframes into packets containing
+ * just one frame.
+ */
+
+#include <stddef.h>
+
+#include "avcodec.h"
+#include "bsf.h"
+#include "bitstream.h"
+#include "bytestream.h"
+
+typedef struct VP9SFSplitContext {
+    AVPacket *buffer_pkt;
+
+    int nb_frames;
+    int next_frame;
+    size_t next_frame_offset;
+    int sizes[8];
+} VP9SFSplitContext;
+
+static int vp9_superframe_split_filter(AVBSFContext *ctx, AVPacket *out)
+{
+    VP9SFSplitContext *s = ctx->priv_data;
+    AVPacket *in;
+    int i, j, ret, marker;
+    int is_superframe = !!s->buffer_pkt;
+
+    if (!s->buffer_pkt) {
+        ret = ff_bsf_get_packet(ctx, &s->buffer_pkt);
+        if (ret < 0)
+            return ret;
+        in = s->buffer_pkt;
+
+        marker = in->data[in->size - 1];
+        if ((marker & 0xe0) == 0xc0) {
+            int length_size = 1 + ((marker >> 3) & 0x3);
+            int   nb_frames = 1 + (marker & 0x7);
+            int    idx_size = 2 + nb_frames * length_size;
+
+            if (in->size >= idx_size && in->data[in->size - idx_size] == marker) {
+                GetByteContext bc;
+                int total_size = 0;
+
+                bytestream2_init(&bc, in->data + in->size + 1 - idx_size,
+                                 nb_frames * length_size);
+
+                for (i = 0; i < nb_frames; i++) {
+                    int frame_size = 0;
+                    for (j = 0; j < length_size; j++)
+                        frame_size |= bytestream2_get_byte(&bc) << (j * 8);
+
+                    total_size += frame_size;
+                    if (total_size > in->size - idx_size) {
+                        av_log(ctx, AV_LOG_ERROR,
+                               "Invalid frame size in a superframe: %d\n", frame_size);
+                        ret = AVERROR(EINVAL);
+                        goto fail;
+                    }
+                    s->sizes[i] = frame_size;
+                }
+                s->nb_frames         = nb_frames;
+                s->next_frame        = 0;
+                s->next_frame_offset = 0;
+                is_superframe        = 1;
+            }
+        }
+    }
+
+    if (is_superframe) {
+        BitstreamContext bc;
+        int profile, invisible = 0;
+
+        ret = av_packet_ref(out, s->buffer_pkt);
+        if (ret < 0)
+            goto fail;
+
+        out->data += s->next_frame_offset;
+        out->size  = s->sizes[s->next_frame];
+
+        s->next_frame_offset += out->size;
+        s->next_frame++;
+
+        if (s->next_frame >= s->nb_frames)
+            av_packet_free(&s->buffer_pkt);
+
+        ret = bitstream_init8(&bc, out->data, out->size);
+        if (ret < 0)
+            goto fail;
+
+        bitstream_read(&bc, 2); // frame_marker
+        profile  = bitstream_read(&bc, 1);
+        profile |= bitstream_read(&bc, 1) << 1;
+        if (profile == 3)
+            bitstream_read(&bc, 1);
+        if (!bitstream_read(&bc, 1)) {
+            bitstream_read(&bc, 1);
+            invisible = !bitstream_read(&bc, 1);
+        }
+
+        if (invisible)
+            out->pts = AV_NOPTS_VALUE;
+
+    } else {
+        av_packet_move_ref(out, s->buffer_pkt);
+        av_packet_free(&s->buffer_pkt);
+    }
+
+    return 0;
+fail:
+    av_packet_free(&s->buffer_pkt);
+    return ret;
+}
+
+static void vp9_superframe_split_uninit(AVBSFContext *ctx)
+{
+    VP9SFSplitContext *s = ctx->priv_data;
+    av_packet_free(&s->buffer_pkt);
+}
+
+const AVBitStreamFilter ff_vp9_superframe_split_bsf = {
+    .name = "vp9_superframe_split",
+    .priv_data_size = sizeof(VP9SFSplitContext),
+    .close          = vp9_superframe_split_uninit,
+    .filter         = vp9_superframe_split_filter,
+    .codec_ids      = (const enum AVCodecID []){ AV_CODEC_ID_VP9, AV_CODEC_ID_NONE },
+};