[FFmpeg-devel] [PATCH 3/4] avcodec: add unpack packed B-frames bitstream filter
Andreas Cadhalpun
andreas.cadhalpun at googlemail.com
Fri Apr 3 19:14:58 CEST 2015
Fixes Ticket #2913
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
---
Changelog | 1 +
doc/bitstream_filters.texi | 20 ++++
libavcodec/Makefile | 1 +
libavcodec/allcodecs.c | 1 +
libavcodec/mpeg4_unpack_bframes_bsf.c | 200 ++++++++++++++++++++++++++++++++++
libavcodec/version.h | 2 +-
patcheck.tmp | 0
7 files changed, 224 insertions(+), 1 deletion(-)
create mode 100644 libavcodec/mpeg4_unpack_bframes_bsf.c
create mode 100644 patcheck.tmp
diff --git a/Changelog b/Changelog
index ba0dff5..a6a0e2d 100644
--- a/Changelog
+++ b/Changelog
@@ -13,6 +13,7 @@ version <next>:
- Intel QSV-accelerated H.264 encoding
- MMAL-accelerated H.264 decoding
- basic APNG encoder and muxer
+- unpack DivX-style packed B-frames in MPEG-4 bitstream filter
version 2.6:
diff --git a/doc/bitstream_filters.texi b/doc/bitstream_filters.texi
index 6431ce8..563049e 100644
--- a/doc/bitstream_filters.texi
+++ b/doc/bitstream_filters.texi
@@ -139,6 +139,26 @@ ffmpeg -i frame_%d.jpg -c:v copy rotated.avi
@section mp3_header_decompress
+ at section mpeg4_unpack_bframes
+
+Unpack DivX-style packed B-frames.
+
+DivX-style packed B-frames are not valid MPEG-4 and were only a
+workaround for the broken Video for Windows subsystem.
+They use more space, can cause minor AV sync issues, require more
+CPU power to decode (unless the player has some decoded picture queue
+to compensate the 2,0,2,0 frame per packet style) and cause
+trouble if copied into a standard container like mp4 or mpeg-ps/ts,
+because MPEG-4 decoders may not be able to decode them, since they are
+not valid MPEG-4.
+
+For example to fix an AVI file containing an MPEG-4 stream with
+DivX-style packed B-frames using @command{ffmpeg}, you can use the command:
+
+ at example
+ffmpeg -i INPUT.avi -codec copy -bsf:v mpeg4_unpack_bframes OUTPUT.avi
+ at end example
+
@section noise
Damages the contents of packets without damaging the container. Can be
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index dd1d850..b01ecd6 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -841,6 +841,7 @@ OBJS-$(CONFIG_H264_MP4TOANNEXB_BSF) += h264_mp4toannexb_bsf.o
OBJS-$(CONFIG_IMX_DUMP_HEADER_BSF) += imx_dump_header_bsf.o
OBJS-$(CONFIG_MJPEG2JPEG_BSF) += mjpeg2jpeg_bsf.o
OBJS-$(CONFIG_MJPEGA_DUMP_HEADER_BSF) += mjpega_dump_header_bsf.o
+OBJS-$(CONFIG_MPEG4_UNPACK_BFRAMES_BSF) += mpeg4_unpack_bframes_bsf.o
OBJS-$(CONFIG_MOV2TEXTSUB_BSF) += movsub_bsf.o
OBJS-$(CONFIG_MP3_HEADER_DECOMPRESS_BSF) += mp3_header_decompress_bsf.o \
mpegaudiodata.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index ef3558a..a3d8c1e 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -605,6 +605,7 @@ void avcodec_register_all(void)
REGISTER_BSF(MJPEG2JPEG, mjpeg2jpeg);
REGISTER_BSF(MJPEGA_DUMP_HEADER, mjpega_dump_header);
REGISTER_BSF(MP3_HEADER_DECOMPRESS, mp3_header_decompress);
+ REGISTER_BSF(MPEG4_UNPACK_BFRAMES, mpeg4_unpack_bframes);
REGISTER_BSF(MOV2TEXTSUB, mov2textsub);
REGISTER_BSF(NOISE, noise);
REGISTER_BSF(REMOVE_EXTRADATA, remove_extradata);
diff --git a/libavcodec/mpeg4_unpack_bframes_bsf.c b/libavcodec/mpeg4_unpack_bframes_bsf.c
new file mode 100644
index 0000000..977e5f0
--- /dev/null
+++ b/libavcodec/mpeg4_unpack_bframes_bsf.c
@@ -0,0 +1,200 @@
+/*
+ * Bitstream filter for unpacking DivX-style packed B-frames in MPEG-4 (divx_packed)
+ * Copyright (c) 2015 Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.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
+ */
+
+#include "avcodec.h"
+#include "get_bits.h"
+#include "mpeg4video.h"
+
+typedef struct UnpackBFramesBSFContext {
+ uint8_t *b_frame_buf;
+ int b_frame_buf_size;
+ int updated_extradata;
+} UnpackBFramesBSFContext;
+
+/* search next start code */
+static unsigned int find_startcode(GetBitContext *gb)
+{
+ unsigned int startcode;
+ align_get_bits(gb);
+ startcode = 0xFF;
+
+ for (; get_bits_count(gb) < gb->size_in_bits;) {
+ startcode = ((startcode << 8) | get_bits(gb, 8)) & 0xFFFFFFFF;
+ if ((startcode & 0xFFFFFF00) != 0x100)
+ continue; /* no startcode */
+ return startcode;
+ }
+
+ return 0;
+}
+
+/* determine the position of the packed marker in the userdata,
+ * the number of VOPs and the position of the second VOP */
+static void scan_buffer(const uint8_t *buf, int buf_size,
+ int *pos_p, int *nb_vop, int *pos_vop2) {
+ GetBitContext gb;
+ unsigned int startcode;
+ int start_pos, i;
+
+ init_get_bits8(&gb, buf, buf_size);
+
+ for (; get_bits_count(&gb) < gb.size_in_bits;) {
+ startcode = find_startcode(&gb);
+
+ if (startcode == USER_DATA_STARTCODE && pos_p) {
+ /* check if the (DivX) userdata string ends with 'p' (packed) */
+ start_pos = get_bits_count(&gb) / 8;
+ for (i = 0; i < 255 && start_pos + i + 1 < buf_size; i++) {
+ if (buf[start_pos + i] == 'p' && buf[start_pos + i + 1] == '\0') {
+ *pos_p = start_pos + i;
+ break;
+ }
+ }
+ } else if (startcode == VOP_STARTCODE && nb_vop) {
+ *nb_vop += 1;
+ if (*nb_vop == 2 && pos_vop2) {
+ *pos_vop2 = get_bits_count(&gb) / 8 - 4; /* subtract 4 bytes startcode */
+ }
+ }
+ }
+}
+
+/* allocate new buffer and copy size bytes from src */
+static uint8_t *create_new_buffer(const uint8_t *src, int size) {
+ uint8_t *dst = av_malloc(size + FF_INPUT_BUFFER_PADDING_SIZE);
+
+ if (dst) {
+ memcpy(dst, src, size);
+ memset(dst + size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
+ }
+
+ return dst;
+}
+
+static int mpeg4_unpack_bframes_filter(AVBitStreamFilterContext *bsfc,
+ AVCodecContext *avctx, const char *args,
+ uint8_t **poutbuf, int *poutbuf_size,
+ const uint8_t *buf, int buf_size,
+ int keyframe)
+{
+ UnpackBFramesBSFContext *ctx = bsfc->priv_data;
+ int pos_p = -1, nb_vop = 0, pos_vop2 = -1, ret = 0;
+
+ if (avctx->codec_id != AV_CODEC_ID_MPEG4) {
+ av_log(avctx, AV_LOG_ERROR,
+ "The mpeg4_unpack_bframes bitstream filter is only useful for mpeg4.\n");
+ return AVERROR(EINVAL);
+ }
+
+ if (!ctx->updated_extradata && avctx->extradata) {
+ int pos_p_ext = -1;
+ scan_buffer(avctx->extradata, avctx->extradata_size, &pos_p_ext, NULL, NULL);
+ if (pos_p_ext >= 0) {
+ av_log(avctx, AV_LOG_DEBUG,
+ "Updating DivX userdata (remove trailing 'p') in extradata.\n");
+ avctx->extradata[pos_p_ext] = '\0';
+ }
+ ctx->updated_extradata = 1;
+ }
+
+ scan_buffer(buf, buf_size, &pos_p, &nb_vop, &pos_vop2);
+ av_log(avctx, AV_LOG_DEBUG, "Found %d VOP startcode(s) in this packet.\n", nb_vop);
+
+ if (pos_vop2 >= 0) {
+ if (ctx->b_frame_buf) {
+ av_log(avctx, AV_LOG_WARNING,
+ "Missing one N-VOP packet, discarding one B-frame.\n");
+ av_freep(&ctx->b_frame_buf);
+ ctx->b_frame_buf_size = 0;
+ }
+ /* store the packed B-frame in the BSFContext */
+ ctx->b_frame_buf_size = buf_size - pos_vop2;
+ ctx->b_frame_buf = create_new_buffer(buf + pos_vop2, ctx->b_frame_buf_size);
+ if (!ctx->b_frame_buf) {
+ ctx->b_frame_buf_size = 0;
+ return AVERROR(ENOMEM);
+ }
+ }
+
+ if (nb_vop > 2) {
+ av_log(avctx, AV_LOG_WARNING,
+ "Found %d VOP headers in one packet, only unpacking one.\n", nb_vop);
+ }
+
+ if (nb_vop == 1 && ctx->b_frame_buf) {
+ /* use frame from BSFContext */
+ *poutbuf = ctx->b_frame_buf;
+ *poutbuf_size = ctx->b_frame_buf_size;
+ /* the output buffer is distinct from the input buffer */
+ ret = 1;
+ if (buf_size < MAX_NVOP_SIZE) {
+ /* N-VOP */
+ av_log(avctx, AV_LOG_DEBUG, "Skipping N-VOP.\n");
+ ctx->b_frame_buf = NULL;
+ ctx->b_frame_buf_size = 0;
+ } else {
+ /* copy packet into BSFContext */
+ ctx->b_frame_buf_size = buf_size;
+ ctx->b_frame_buf = create_new_buffer(buf , buf_size);
+ if (!ctx->b_frame_buf) {
+ ctx->b_frame_buf_size = 0;
+ av_freep(poutbuf);
+ *poutbuf_size = 0;
+ return AVERROR(ENOMEM);
+ }
+ }
+ } else if (nb_vop >= 2) {
+ /* use first frame of the packet */
+ *poutbuf = (uint8_t *) buf;
+ *poutbuf_size = pos_vop2;
+ } else if (pos_p >= 0) {
+ av_log(avctx, AV_LOG_DEBUG, "Updating DivX userdata (remove trailing 'p').\n");
+ *poutbuf_size = buf_size;
+ *poutbuf = create_new_buffer(buf, buf_size);
+ if (!*poutbuf) {
+ *poutbuf_size = 0;
+ return AVERROR(ENOMEM);
+ }
+ /* remove 'p' (packed) from the end of the (DivX) userdata string */
+ (*poutbuf)[pos_p] = '\0';
+ /* the output buffer is distinct from the input buffer */
+ ret = 1;
+ } else {
+ /* copy packet */
+ *poutbuf = (uint8_t *) buf;
+ *poutbuf_size = buf_size;
+ }
+
+ return ret;
+}
+
+static void mpeg4_unpack_bframes_close(AVBitStreamFilterContext *bsfc)
+{
+ UnpackBFramesBSFContext *ctx = bsfc->priv_data;
+ av_freep(&ctx->b_frame_buf);
+}
+
+AVBitStreamFilter ff_mpeg4_unpack_bframes_bsf = {
+ .name = "mpeg4_unpack_bframes",
+ .priv_data_size = sizeof(UnpackBFramesBSFContext),
+ .filter = mpeg4_unpack_bframes_filter,
+ .close = mpeg4_unpack_bframes_close
+};
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 19d3993..dcb9652 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -29,7 +29,7 @@
#include "libavutil/version.h"
#define LIBAVCODEC_VERSION_MAJOR 56
-#define LIBAVCODEC_VERSION_MINOR 33
+#define LIBAVCODEC_VERSION_MINOR 34
#define LIBAVCODEC_VERSION_MICRO 100
#define LIBAVCODEC_VERSION_INT AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
diff --git a/patcheck.tmp b/patcheck.tmp
new file mode 100644
index 0000000..e69de29
--
2.1.4
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