ifndef AV_WB32
define AV_WB32(p, val) do { \
uint32_t d = (val); \((uint8_t*)(p))[3] = (d); \((uint8_t*)(p))[2] = (d)>>8; \((uint8_t*)(p))[1] = (d)>>16; \((uint8_t*)(p))[0] = (d)>>24; \} while(0)
endif
ifndef AV_RB16
define AV_RB16(x) \
((((const uint8_t*)(x))[0] << 8) | \((const uint8_t*)(x))[1])
endif
int h264_exradata_to_annexb(const uint8_t codec_extradata, const int codec_extradata_size, AVPacket out_extradata, int padding) { uint16_t unit_size; uint64_t total_size = 0; uint8_t out = NULL, unit_nb, sps_done = 0, sps_seen = 0, pps_seen = 0, pps_len = 0, sps_offset = 0, pps_offset = 0; const uint8_t extradata = codec_extradata + 4; //扩展数据的前4个字节无用，直接跳过 static const uint8_t nalu_header[4] = {0, 0, 0, 1}; int length_size = (*extradata++ & 0x3) + 1; //表示sps和pps的长度所占的字节数,一般是2个
sps_offset = pps_offset = -1;unit_nb = *extradata++ & 0x1f; //sps和pps的个数if (!unit_nb) {goto pps;} else {sps_offset = 0;sps_seen = 1;}//遍历每个sps和ppswhile (unit_nb--) {int err;unit_size = AV_RB16(extradata); //获取sps和pps的长度total_size += unit_size + 4; //+startcodeif (total_size > INT_MAX - padding) {av_log(NULL, AV_LOG_ERROR, "Too big extradata size, corrupted stream or invalid MP4/AVCC bitstream\n");av_free(out);return AVERROR(EINVAL);}if (extradata+2+unit_size > codec_extradata+codec_extradata_size) {av_log(NULL, AV_LOG_ERROR, "Packet header is not contained in global extradata""corrupted stream or invalid MP4/AVCC bitstream\n");av_free(out);return AVERROR(EINVAL);}//重新分配长度if ((err = av_reallocp(&out, total_size+padding)) < 0)return err;memcpy(out+total_size-unit_size-4, nalu_header, 4);memcpy(out+total_size-unit_size, extradata+2, unit_size);extradata += 2 + unit_size;
pps: if (!unit_nb && !sps_done++) { unit_nb = *extradata++; if (unit_nb) { pps_offset = total_size; sps_seen = 1; } } } if (out) { memset(out+total_size, 0, padding); }
if (!sps_seen) {av_log(NULL, AV_LOG_WARNING, "Warning:SPS NALU missing or invalid.""The resulting stream may not play.\n");}if (!pps_seen) {av_log(NULL, AV_LOG_WARNING, "Warning:PPS NALU missing or invalid.""The resulting stream may not play.\n");}out_extradata->data = out;out_extradata->size = total_size;return length_size;
}
static int alloc_and_copy(AVPacket out, const uint8_t sps_pps, uint32_t sps_pps_size, const uint8_t *in, uint32_t in_size) { uint32_t offset = out->size; uint8_t nal_header_size = offset ? 3 : 4; int err;
//对avpacket进行扩容err = av_grow_packet(out, sps_pps_size+in_size+nal_header_size);if (err) {return err;}if (sps_pps)memcpy(out->data+offset, sps_pps, sps_pps_size);memcpy(out->data+sps_pps_size+nal_header_size+offset, in, in_size);if (!offset) {AV_WB32(out->data+sps_pps_size, 1);} else {(out->data + offset + sps_pps_size)[0] = 0;(out->data + offset + sps_pps_size)[0] = 0;(out->data + offset + sps_pps_size)[0] = 1;}return 0;
} int h264_mp4toannexb(AVFormatContext fmt_ctx, AVPacket in, FILE dst_fd) { AVPacket out = NULL; AVPacket spspps_pkt;
int len = 0;uint8_t unit_type;uint32_t nal_size;uint32_t cumul_size = 0;const uint8_t *buf = NULL;const uint8_t *buf_end = NULL;int buf_size;int ret = 0, i = 0;out = av_packet_alloc(); //此时out->size == 0buf = in->data;buf_size = in->size;buf_end = in->data + in->size;do {ret = AVERROR(EINVAL);if (buf + 4 > buf_end) {goto fail;}//pkt.data的前四个字节是一帧数据的大小; 如果是存放多帧的话，先取4个字节的帧大小取帧数据，再取4个字节帧大小，取帧数据，以此类推for (nal_size = 0, i = 0; i<4; i++) {nal_size = (nal_size << 8) | buf[i];}buf += 4;unit_type = *buf & 0x1f;if (nal_size > buf_end - buf || nal_size < 0)goto fail;//如果是关键帧，需要添加sps和pps在关键帧数据前if (unit_type == 5) {h264_exradata_to_annexb(fmt_ctx->streams[in->stream_index]->codec->extradata,fmt_ctx->streams[in->stream_index]->codec->extradata_size,&spspps_pkt,AV_INPUT_BUFFER_PADDING_SIZE);if ((ret = alloc_and_copy(out,spspps_pkt.data, spspps_pkt.size,buf, nal_size)) < 0) {goto fail;}} else {if ((ret = alloc_and_copy(out, NULL, 0, buf, nal_size)) < 0)goto fail;}len = fwrite(out->data, 1, out->size, dst_fd);if (len != out->size) {av_log(NULL, AV_LOG_DEBUG, "warning, length of writed data isn't equal pkt.size(%d, %d)\n",len,out->size);}fflush(dst_fd);
next_nal: buf += nal_size; cumul_size += nal_size + 4; } while (cumul_size < buf_size);
fail: av_packet_free(&out);
return ret;
} int main(int argc, char *argv[]) { int err_code; char errors[1024];
char *src_filename = NULL;char *dst_filename = NULL;FILE *dst_fd = NULL;int video_stream_index = -1;AVFormatContext *fmt_ctx = NULL;AVPacket pkt;av_log_set_level(AV_LOG_DEBUG);if (argc < 3) {av_log(NULL, AV_LOG_DEBUG, "the count of paramers should be more than three!\n");return -1;}src_filename = argv[1];dst_filename = argv[2];if (src_filename == NULL || dst_filename == NULL) {av_log(NULL, AV_LOG_DEBUG, "src or dst file is null, plz check them!\n");return -1;}//register all formats and codecav_register_all();dst_fd = fopen(dst_filename, "wb");if (!dst_fd) {av_log(NULL, AV_LOG_DEBUG, "Could not open destination file %s\n", dst_filename);return -1;}if ((err_code = avformat_open_input(&fmt_ctx, src_filename, NULL, NULL)) < 0) {av_strerror(err_code, errors, 1024);av_log(NULL, AV_LOG_DEBUG, "Could not open source file: %s, %d(%s)\n",src_filename,err_code,errors);return -1;}av_dump_format(fmt_ctx, 0, src_filename, 0);av_init_packet(&pkt);pkt.data = NULL;pkt.size = 0;video_stream_index = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);if (video_stream_index < 0) {av_log(NULL, AV_LOG_DEBUG, "Could not find %s stream in input file %s\n",av_get_media_type_string(AVMEDIA_TYPE_VIDEO),src_filename);return AVERROR(EINVAL);}while (av_read_frame(fmt_ctx, &pkt) >=0) {if (pkt.stream_index == video_stream_index) {h264_mp4toannexb(fmt_ctx, &pkt, dst_fd);}av_packet_unref(&pkt);}av_packet_unref(&pkt);if (fmt_ctx) {avformat_close_input(&fmt_ctx);fmt_ctx = NULL;}if (dst_fd) {fclose(dst_fd);dst_fd = NULL;}return 0;
}
```
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