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![erankor](/assets/img/avatar_default.png)
support writing encrypted mp4 using aes-ctr, conforming to ISO/IEC 23001-7. 3 new parameters were added: - encryption_scheme - allowed values are none (default) and cenc-aes-ctr - encryption_key - 128 bit encryption key (hex) - encryption_kid - 128 bit encryption key identifier (hex) Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
416 lines
11 KiB
C
416 lines
11 KiB
C
/*
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* MOV CENC (Common Encryption) writer
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* Copyright (c) 2015 Eran Kornblau <erankor at gmail dot 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 "movenccenc.h"
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#include "libavutil/intreadwrite.h"
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#include "avio_internal.h"
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#include "movenc.h"
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#include "avc.h"
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static int auxiliary_info_alloc_size(MOVMuxCencContext* ctx, int size)
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{
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size_t new_alloc_size;
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if (ctx->auxiliary_info_size + size > ctx->auxiliary_info_alloc_size) {
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new_alloc_size = FFMAX(ctx->auxiliary_info_size + size, ctx->auxiliary_info_alloc_size * 2);
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if (av_reallocp(&ctx->auxiliary_info, new_alloc_size)) {
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return AVERROR(ENOMEM);
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}
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ctx->auxiliary_info_alloc_size = new_alloc_size;
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}
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return 0;
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}
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static int auxiliary_info_write(MOVMuxCencContext* ctx,
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const uint8_t *buf_in, int size)
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{
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int ret;
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ret = auxiliary_info_alloc_size(ctx, size);
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if (ret) {
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return ret;
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}
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memcpy(ctx->auxiliary_info + ctx->auxiliary_info_size, buf_in, size);
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ctx->auxiliary_info_size += size;
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return 0;
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}
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static int auxiliary_info_add_subsample(MOVMuxCencContext* ctx,
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uint16_t clear_bytes, uint32_t encrypted_bytes)
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{
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uint8_t* p;
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int ret;
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if (!ctx->use_subsamples) {
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return 0;
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}
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ret = auxiliary_info_alloc_size(ctx, 6);
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if (ret) {
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return ret;
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}
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p = ctx->auxiliary_info + ctx->auxiliary_info_size;
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AV_WB16(p, clear_bytes);
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p += sizeof(uint16_t);
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AV_WB32(p, encrypted_bytes);
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ctx->auxiliary_info_size += 6;
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ctx->subsample_count++;
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return 0;
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}
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/**
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* Encrypt the input buffer and write using avio_write
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*/
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static void mov_cenc_write_encrypted(MOVMuxCencContext* ctx, AVIOContext *pb,
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const uint8_t *buf_in, int size)
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{
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uint8_t chunk[4096];
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const uint8_t* cur_pos = buf_in;
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int size_left = size;
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int cur_size;
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while (size_left > 0) {
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cur_size = FFMIN(size_left, sizeof(chunk));
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av_aes_ctr_crypt(ctx->aes_ctr, chunk, cur_pos, cur_size);
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avio_write(pb, chunk, cur_size);
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cur_pos += cur_size;
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size_left -= cur_size;
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}
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}
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/**
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* Start writing a packet
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*/
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static int mov_cenc_start_packet(MOVMuxCencContext* ctx)
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{
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int ret;
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/* write the iv */
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ret = auxiliary_info_write(ctx, av_aes_ctr_get_iv(ctx->aes_ctr), AES_CTR_IV_SIZE);
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if (ret) {
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return ret;
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}
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if (!ctx->use_subsamples) {
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return 0;
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}
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/* write a zero subsample count */
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ctx->auxiliary_info_subsample_start = ctx->auxiliary_info_size;
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ctx->subsample_count = 0;
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ret = auxiliary_info_write(ctx, (uint8_t*)&ctx->subsample_count, sizeof(ctx->subsample_count));
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if (ret) {
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return ret;
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}
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return 0;
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}
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/**
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* Finalize a packet
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*/
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static int mov_cenc_end_packet(MOVMuxCencContext* ctx)
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{
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size_t new_alloc_size;
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av_aes_ctr_increment_iv(ctx->aes_ctr);
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if (!ctx->use_subsamples) {
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ctx->auxiliary_info_entries++;
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return 0;
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}
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/* add the auxiliary info entry size*/
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if (ctx->auxiliary_info_entries >= ctx->auxiliary_info_sizes_alloc_size) {
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new_alloc_size = ctx->auxiliary_info_entries * 2 + 1;
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if (av_reallocp(&ctx->auxiliary_info_sizes, new_alloc_size)) {
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return AVERROR(ENOMEM);
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}
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ctx->auxiliary_info_sizes_alloc_size = new_alloc_size;
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}
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ctx->auxiliary_info_sizes[ctx->auxiliary_info_entries] =
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AES_CTR_IV_SIZE + ctx->auxiliary_info_size - ctx->auxiliary_info_subsample_start;
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ctx->auxiliary_info_entries++;
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/* update the subsample count*/
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AV_WB16(ctx->auxiliary_info + ctx->auxiliary_info_subsample_start, ctx->subsample_count);
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return 0;
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}
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int ff_mov_cenc_write_packet(MOVMuxCencContext* ctx, AVIOContext *pb,
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const uint8_t *buf_in, int size)
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{
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int ret;
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ret = mov_cenc_start_packet(ctx);
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if (ret) {
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return ret;
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}
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ret = auxiliary_info_add_subsample(ctx, 0, size);
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if (ret) {
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return ret;
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}
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mov_cenc_write_encrypted(ctx, pb, buf_in, size);
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ret = mov_cenc_end_packet(ctx);
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if (ret) {
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return ret;
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}
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return 0;
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}
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int ff_mov_cenc_avc_parse_nal_units(MOVMuxCencContext* ctx, AVIOContext *pb,
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const uint8_t *buf_in, int size)
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{
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const uint8_t *p = buf_in;
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const uint8_t *end = p + size;
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const uint8_t *nal_start, *nal_end;
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int ret;
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ret = mov_cenc_start_packet(ctx);
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if (ret) {
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return ret;
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}
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size = 0;
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nal_start = ff_avc_find_startcode(p, end);
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for (;;) {
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while (nal_start < end && !*(nal_start++));
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if (nal_start == end)
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break;
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nal_end = ff_avc_find_startcode(nal_start, end);
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avio_wb32(pb, nal_end - nal_start);
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avio_w8(pb, *nal_start);
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mov_cenc_write_encrypted(ctx, pb, nal_start + 1, nal_end - nal_start - 1);
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auxiliary_info_add_subsample(ctx, 5, nal_end - nal_start - 1);
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size += 4 + nal_end - nal_start;
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nal_start = nal_end;
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}
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ret = mov_cenc_end_packet(ctx);
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if (ret) {
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return ret;
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}
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return size;
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}
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int ff_mov_cenc_avc_write_nal_units(AVFormatContext *s, MOVMuxCencContext* ctx,
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int nal_length_size, AVIOContext *pb, const uint8_t *buf_in, int size)
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{
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int nalsize;
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int ret;
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int j;
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ret = mov_cenc_start_packet(ctx);
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if (ret) {
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return ret;
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}
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while (size > 0) {
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/* parse the nal size */
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if (size < nal_length_size + 1) {
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av_log(s, AV_LOG_ERROR, "CENC-AVC: remaining size %d smaller than nal length+type %d\n",
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size, nal_length_size + 1);
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return -1;
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}
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avio_write(pb, buf_in, nal_length_size + 1);
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nalsize = 0;
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for (j = 0; j < nal_length_size; j++) {
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nalsize = (nalsize << 8) | *buf_in++;
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}
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size -= nal_length_size;
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/* encrypt the nal body */
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if (nalsize <= 0 || nalsize > size) {
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av_log(s, AV_LOG_ERROR, "CENC-AVC: nal size %d remaining %d\n", nalsize, size);
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return -1;
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}
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mov_cenc_write_encrypted(ctx, pb, buf_in + 1, nalsize - 1);
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buf_in += nalsize;
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size -= nalsize;
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auxiliary_info_add_subsample(ctx, nal_length_size + 1, nalsize - 1);
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}
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ret = mov_cenc_end_packet(ctx);
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if (ret) {
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return ret;
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}
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return 0;
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}
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/* TODO: reuse this function from movenc.c */
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static int64_t update_size(AVIOContext *pb, int64_t pos)
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{
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int64_t curpos = avio_tell(pb);
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avio_seek(pb, pos, SEEK_SET);
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avio_wb32(pb, curpos - pos); /* rewrite size */
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avio_seek(pb, curpos, SEEK_SET);
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return curpos - pos;
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}
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static int mov_cenc_write_senc_tag(MOVMuxCencContext* ctx, AVIOContext *pb,
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int64_t* auxiliary_info_offset)
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{
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int64_t pos = avio_tell(pb);
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avio_wb32(pb, 0); /* size */
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ffio_wfourcc(pb, "senc");
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avio_wb32(pb, ctx->use_subsamples ? 0x02 : 0); /* version & flags */
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avio_wb32(pb, ctx->auxiliary_info_entries); /* entry count */
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*auxiliary_info_offset = avio_tell(pb);
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avio_write(pb, ctx->auxiliary_info, ctx->auxiliary_info_size);
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return update_size(pb, pos);
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}
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static int mov_cenc_write_saio_tag(AVIOContext *pb, int64_t auxiliary_info_offset)
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{
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int64_t pos = avio_tell(pb);
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uint8_t version;
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avio_wb32(pb, 0); /* size */
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ffio_wfourcc(pb, "saio");
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version = auxiliary_info_offset > 0xffffffff ? 1 : 0;
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avio_w8(pb, version);
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avio_wb24(pb, 0); /* flags */
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avio_wb32(pb, 1); /* entry count */
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if (version) {
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avio_wb64(pb, auxiliary_info_offset);
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} else {
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avio_wb32(pb, auxiliary_info_offset);
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}
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return update_size(pb, pos);
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}
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static int mov_cenc_write_saiz_tag(MOVMuxCencContext* ctx, AVIOContext *pb)
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{
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int64_t pos = avio_tell(pb);
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avio_wb32(pb, 0); /* size */
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ffio_wfourcc(pb, "saiz");
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avio_wb32(pb, 0); /* version & flags */
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avio_w8(pb, ctx->use_subsamples ? 0 : AES_CTR_IV_SIZE); /* default size*/
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avio_wb32(pb, ctx->auxiliary_info_entries); /* entry count */
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if (ctx->use_subsamples) {
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avio_write(pb, ctx->auxiliary_info_sizes, ctx->auxiliary_info_entries);
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}
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return update_size(pb, pos);
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}
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void ff_mov_cenc_write_stbl_atoms(MOVMuxCencContext* ctx, AVIOContext *pb)
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{
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int64_t auxiliary_info_offset;
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mov_cenc_write_senc_tag(ctx, pb, &auxiliary_info_offset);
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mov_cenc_write_saio_tag(pb, auxiliary_info_offset);
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mov_cenc_write_saiz_tag(ctx, pb);
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}
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static int mov_cenc_write_schi_tag(AVIOContext *pb, uint8_t* kid)
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{
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int64_t pos = avio_tell(pb);
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avio_wb32(pb, 0); /* size */
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ffio_wfourcc(pb, "schi");
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avio_wb32(pb, 32); /* size */
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ffio_wfourcc(pb, "tenc");
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avio_wb32(pb, 0); /* version & flags */
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avio_wb24(pb, 1); /* is encrypted */
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avio_w8(pb, AES_CTR_IV_SIZE); /* iv size */
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avio_write(pb, kid, CENC_KID_SIZE);
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return update_size(pb, pos);
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}
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int ff_mov_cenc_write_sinf_tag(MOVTrack* track, AVIOContext *pb, uint8_t* kid)
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{
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int64_t pos = avio_tell(pb);
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avio_wb32(pb, 0); /* size */
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ffio_wfourcc(pb, "sinf");
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/* frma */
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avio_wb32(pb, 12); /* size */
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ffio_wfourcc(pb, "frma");
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avio_wl32(pb, track->tag);
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/* schm */
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avio_wb32(pb, 20); /* size */
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ffio_wfourcc(pb, "schm");
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avio_wb32(pb, 0); /* version & flags */
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ffio_wfourcc(pb, "cenc"); /* scheme type*/
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avio_wb32(pb, 0x10000); /* scheme version */
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/* schi */
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mov_cenc_write_schi_tag(pb, kid);
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return update_size(pb, pos);
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}
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int ff_mov_cenc_init(MOVMuxCencContext* ctx, uint8_t* encryption_key,
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int use_subsamples, int bitexact)
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{
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int ret;
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ctx->aes_ctr = av_aes_ctr_alloc();
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if (!ctx->aes_ctr) {
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return AVERROR(ENOMEM);
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}
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ret = av_aes_ctr_init(ctx->aes_ctr, encryption_key);
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if (ret != 0) {
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return ret;
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}
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if (!bitexact) {
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av_aes_ctr_set_random_iv(ctx->aes_ctr);
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}
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ctx->use_subsamples = use_subsamples;
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return 0;
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}
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void ff_mov_cenc_free(MOVMuxCencContext* ctx)
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{
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av_aes_ctr_free(ctx->aes_ctr);
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}
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