---------------------------------------------------------------- 更改视频格式流程 ----------------------------------------------------------------
解码后的数据存储在data[0]、data[1]、data[2]中,
data[0]存储了linesize[0] * height个数据,
为对齐解码器的CPU及其他优化等原因,导致linesize[0],实际上并不等于宽度width, 而是比宽度大。
linesize[0] - Y分量对应的一个宽度
1、av_parse_video_size -- 解析分辨率
2、sws_getContext -- 获得分辨率切换的上下文
3、av_frame_alloc -- 图像转换后的数据需要存储起来
4、av_image_get_buffer_size -- 共创建多少字节的空间
5、av_malloc -- 创建【申请空间】
6、av_image_fill_arrays -- 格式化分配空间
7、sws_scale -- 视频处理
sws_scale() 函数 -- 清空无效数据
1、图像色彩空间转换;
2、分辨率缩放
3、前后图像滤波处理
int ChangeResolutionInterface(AVCodecContext *codecCtx, AVPacket *packet, struct SwsContext *swsCtx, int destWidth, int destHeight, AVFrame *destFrame, FILE *dest_fp, int *frameCount)
{
AVFrame *frame = av_frame_alloc();
if (frame == NULL)
{
av_log(NULL, AV_LOG_ERROR, "frame alloc failed!\n");
}
int ret = avcodec_send_packet(codecCtx, packet);
if (ret != 0)
{
av_log(NULL, AV_LOG_ERROR, "send packet failed:%s\n", av_err2str(ret));
av_packet_unref(packet);
return -1;
}
while (avcodec_receive_frame(codecCtx, frame) == 0)
{
sws_scale(swsCtx, (const uint8_t *const *)frame->data, frame->linesize, 0, codecCtx->height, destFrame->data, destFrame->linesize); // 视频处理
// 保存 sws_scale 处理后的 帧
fwrite(destFrame->data[0], 1, destWidth * destHeight, dest_fp);
fwrite(destFrame->data[1], 1, destWidth * destHeight / 4, dest_fp);
fwrite(destFrame->data[2], 1, destWidth * destHeight / 4, dest_fp);
(*frameCount)++;
av_log(NULL, AV_LOG_DEBUG, "frameCount = %d, linesize[0] = %d, linesize[1] = %d, linesize[2] = %d, width = %d, heigth = %d\n",
*frameCount, destFrame->linesize[0], destFrame->linesize[1], destFrame->linesize[2], destWidth, destHeight);
}
if (frame)
{
av_frame_free(&frame);
}
}
int ChangeResolutionDecodeVideoYUV(const char *inFileName, const char *outFileName, char *destVideoSizeString)
{
int frameCount = 0;
/**********************************************************************************/
FILE *dest_fp = fopen(outFileName, "wb+");
if (dest_fp == NULL)
{
av_log(NULL, AV_LOG_ERROR, "open outfile:%s failed!\n", outFileName);
return -1;
}
/**********************************************************************************/
// 分析分辨率
int destWidth ,destHeight;
int ret = av_parse_video_size(&destWidth, &destHeight, destVideoSizeString); // 解析分辨率
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "invalid video size: %s\n", destVideoSizeString);
return -1;
}
av_log(NULL, AV_LOG_INFO, "destWidth:%d, destHeight:%d\n", destWidth, destHeight);
AVFormatContext *inFmtCtx = NULL;
ret = avformat_open_input(&inFmtCtx, inFileName, NULL, NULL);
if (ret != 0)
{
av_log(NULL, AV_LOG_ERROR, "open input file error\n");
return -1;
}
ret = avformat_find_stream_info(inFmtCtx, NULL);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "find stream info error\n");
goto fail;
}
int videoStreamIndex = av_find_best_stream(inFmtCtx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
if (videoStreamIndex < 0)
{
av_log(NULL, AV_LOG_ERROR, "alloc avcodec context failed!\n");
goto fail;
}
AVCodecContext *codecCtx = avcodec_alloc_context3(NULL);
if (codecCtx == NULL)
{
av_log(NULL, AV_LOG_ERROR, "alloc avcodec context failed!\n");
goto fail;
}
avcodec_parameters_to_context(codecCtx, inFmtCtx->streams[videoStreamIndex]->codecpar);
AVCodec *decoder = avcodec_find_decoder(codecCtx->codec_id);
if (decoder == NULL)
{
av_log(NULL, AV_LOG_ERROR, "find decoder failed,codec_id:%d\n", codecCtx->codec_id);
ret = -1;
goto fail;
}
ret = avcodec_open2(codecCtx, decoder, NULL);
if (ret != 0)
{
av_log(NULL, AV_LOG_ERROR, "open decoder failed:%s \n", av_err2str(ret));
ret = -1;
goto fail;
}
// 获得分辨率切换的上下文
enum AVPixelFormat destPixFormat = codecCtx->pix_fmt;
struct SwsContext *swsCtx = sws_getContext(codecCtx->width, codecCtx->height, codecCtx->pix_fmt,
destWidth, destHeight, destPixFormat,
SWS_FAST_BILINEAR, NULL, NULL, NULL);
if (swsCtx == NULL)
{
av_log(NULL, AV_LOG_ERROR, "get sws context failed!\n");
ret = -1;
goto fail;
}
AVFrame *destFrame = av_frame_alloc(); // 图像转换后的数据需要存储起来
uint8_t *outBuffer = av_malloc(av_image_get_buffer_size(destPixFormat, destWidth, destHeight, 1) /*共创建多少字节的空间*/);
av_image_fill_arrays(destFrame->data, destFrame->linesize, outBuffer, destPixFormat, destWidth, destHeight, 1); // 格式化分配空间
AVPacket packet;
av_init_packet(&packet);
while (av_read_frame(inFmtCtx, &packet) >= 0)
{
if (packet.stream_index == videoStreamIndex)
{
if (ChangeResolutionInterface(codecCtx, &packet, swsCtx, destWidth, destHeight, destFrame, dest_fp, &frameCount) == -1)
{
ret = -1;
av_packet_unref(&packet);
goto fail;
}
}
av_packet_unref(&packet);
}
// flush decoder
ChangeResolutionInterface(codecCtx, NULL, swsCtx, destWidth, destHeight, destFrame, dest_fp, &frameCount);
fail:
if (inFmtCtx)
{
av_log(NULL, AV_LOG_DEBUG, "inFmtCtx format close input\n");
avformat_close_input(&inFmtCtx);
}
if (codecCtx)
{
av_log(NULL, AV_LOG_DEBUG, "codecCtx codec free context\n");
avcodec_free_context(&codecCtx);
}
if (dest_fp)
{
av_log(NULL, AV_LOG_DEBUG, "dest_fp fclose\n");
fclose(dest_fp);
}
if (destFrame)
{
av_log(NULL, AV_LOG_DEBUG, "destFrame av frame free\n");
av_frame_free(&destFrame);
}
if (outBuffer)
{
av_log(NULL, AV_LOG_DEBUG, "outBuffer free\n");
av_free(outBuffer);
}
return ret;
}