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/* |
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* Bitstream filter for unpacking DivX-style packed B-frames in MPEG-4 (divx_packed) |
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* Copyright (c) 2015 Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com> |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#include "bsf.h" |
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#include "bsf_internal.h" |
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#include "internal.h" |
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#include "mpeg4video.h" |
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typedef struct UnpackBFramesBSFContext { |
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AVBufferRef *b_frame_ref; |
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} UnpackBFramesBSFContext; |
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/* determine the position of the packed marker in the userdata, |
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* the number of VOPs and the position of the second VOP */ |
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static void scan_buffer(const uint8_t *buf, int buf_size, |
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int *pos_p, int *nb_vop, int *pos_vop2) { |
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uint32_t startcode; |
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const uint8_t *end = buf + buf_size, *pos = buf; |
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✓✓ |
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while (pos < end) { |
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startcode = -1; |
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pos = avpriv_find_start_code(pos, end, &startcode); |
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✓✓✓✗
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if (startcode == USER_DATA_STARTCODE && pos_p) { |
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/* check if the (DivX) userdata string ends with 'p' (packed) */ |
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✓✓✓✓
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for (int i = 0; i < 255 && pos + i + 1 < end; i++) { |
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✓✓✓✓
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if (pos[i] == 'p' && pos[i + 1] == '\0') { |
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*pos_p = pos + i - buf; |
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break; |
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} |
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} |
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✓✓✓✗
|
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} else if (startcode == VOP_STARTCODE && nb_vop) { |
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*nb_vop += 1; |
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✓✓✓✗
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if (*nb_vop == 2 && pos_vop2) { |
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*pos_vop2 = pos - buf - 4; /* subtract 4 bytes startcode */ |
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} |
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} |
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} |
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} |
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static int mpeg4_unpack_bframes_filter(AVBSFContext *ctx, AVPacket *pkt) |
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{ |
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UnpackBFramesBSFContext *s = ctx->priv_data; |
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int pos_p = -1, nb_vop = 0, pos_vop2 = -1, ret = 0; |
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ret = ff_bsf_get_packet_ref(ctx, pkt); |
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✓✓ |
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if (ret < 0) |
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return ret; |
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scan_buffer(pkt->data, pkt->size, &pos_p, &nb_vop, &pos_vop2); |
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av_log(ctx, AV_LOG_DEBUG, "Found %d VOP startcode(s) in this packet.\n", nb_vop); |
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✓✓ |
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if (pos_vop2 >= 0) { |
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✗✓ |
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if (s->b_frame_ref) { |
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av_log(ctx, AV_LOG_WARNING, |
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"Missing one N-VOP packet, discarding one B-frame.\n"); |
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av_buffer_unref(&s->b_frame_ref); |
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} |
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/* store a reference to the packed B-frame's data in the BSFContext */ |
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s->b_frame_ref = av_buffer_ref(pkt->buf); |
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✗✓ |
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if (!s->b_frame_ref) { |
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ret = AVERROR(ENOMEM); |
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goto fail; |
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} |
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s->b_frame_ref->data = pkt->data + pos_vop2; |
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s->b_frame_ref->size = pkt->size - pos_vop2; |
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} |
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✗✓ |
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if (nb_vop > 2) { |
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av_log(ctx, AV_LOG_WARNING, |
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"Found %d VOP headers in one packet, only unpacking one.\n", nb_vop); |
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} |
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✓✓✓✓
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if (nb_vop == 1 && s->b_frame_ref) { |
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AVBufferRef *tmp = pkt->buf; |
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/* make tmp accurately reflect the packet's data */ |
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tmp->data = pkt->data; |
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tmp->size = pkt->size; |
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/* replace data in packet with stored data */ |
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pkt->buf = s->b_frame_ref; |
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pkt->data = s->b_frame_ref->data; |
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pkt->size = s->b_frame_ref->size; |
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/* store reference to data into BSFContext */ |
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s->b_frame_ref = tmp; |
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✓✓ |
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if (s->b_frame_ref->size <= MAX_NVOP_SIZE) { |
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/* N-VOP - discard stored data */ |
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av_log(ctx, AV_LOG_DEBUG, "Skipping N-VOP.\n"); |
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av_buffer_unref(&s->b_frame_ref); |
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} |
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✓✓ |
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} else if (nb_vop >= 2) { |
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/* use first frame of the packet */ |
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pkt->size = pos_vop2; |
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✓✓ |
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} else if (pos_p >= 0) { |
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ret = av_packet_make_writable(pkt); |
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✗✓ |
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if (ret < 0) |
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goto fail; |
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av_log(ctx, AV_LOG_DEBUG, "Updating DivX userdata (remove trailing 'p').\n"); |
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/* remove 'p' (packed) from the end of the (DivX) userdata string */ |
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pkt->data[pos_p] = '\0'; |
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} else { |
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/* use packet as is */ |
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} |
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fail: |
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✗✓ |
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if (ret < 0) |
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av_packet_unref(pkt); |
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return ret; |
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} |
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static int mpeg4_unpack_bframes_init(AVBSFContext *ctx) |
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{ |
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✓✗ |
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if (ctx->par_in->extradata) { |
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int pos_p_ext = -1; |
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scan_buffer(ctx->par_in->extradata, ctx->par_in->extradata_size, &pos_p_ext, NULL, NULL); |
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✓✗ |
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if (pos_p_ext >= 0) { |
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av_log(ctx, AV_LOG_DEBUG, |
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"Updating DivX userdata (remove trailing 'p') in extradata.\n"); |
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ctx->par_out->extradata[pos_p_ext] = '\0'; |
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} |
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} |
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return 0; |
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} |
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static void mpeg4_unpack_bframes_close_flush(AVBSFContext *bsfc) |
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{ |
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UnpackBFramesBSFContext *ctx = bsfc->priv_data; |
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av_buffer_unref(&ctx->b_frame_ref); |
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} |
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static const enum AVCodecID codec_ids[] = { |
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AV_CODEC_ID_MPEG4, AV_CODEC_ID_NONE, |
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}; |
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const AVBitStreamFilter ff_mpeg4_unpack_bframes_bsf = { |
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.name = "mpeg4_unpack_bframes", |
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.priv_data_size = sizeof(UnpackBFramesBSFContext), |
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.init = mpeg4_unpack_bframes_init, |
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.filter = mpeg4_unpack_bframes_filter, |
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.flush = mpeg4_unpack_bframes_close_flush, |
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.close = mpeg4_unpack_bframes_close_flush, |
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.codec_ids = codec_ids, |
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}; |