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4 详细设计
这章是FFMPEG C++封装库的详细设计。
4.1 Init
该模块初始化FFMPEG库。
4.1.1 Init定义
namespace media
{
namespace sdk
{
void MEDIASDK_EXPORT Init();
}
}
函数说明：
- Init 初始化FFMPEG库，该函数可调用多次。
4.1.2 Init实现
namespace media
{
namespace sdk
{
void Init()
{static bool isInit = false;if(isInit)return;isInit = true;avcodec_register_all();avfilter_register_all();av_register_all();avformat_network_init();Report(false);
}
}
}
函数流程：
- 注册支持的全部编码器(codec)。
- 注册支持的全部过滤器(filter)。
- 注册支持的全部封包格式（format）。
- 初始化支持的网络。
- 默认关闭打印输出。
4.2 Utils
该模块提供FFMPEG库的工具函数。
4.2.1 Utils定义
namespace media
{
namespace sdk
{
void MEDIASDK_EXPORT Report(bool on);void MEDIASDK_EXPORT Formats();
void MEDIASDK_EXPORT Codecs(bool encoder);
void MEDIASDK_EXPORT Bsfs();
void MEDIASDK_EXPORT Protocols();
void MEDIASDK_EXPORT Filters();
void MEDIASDK_EXPORT PixFmts();
void MEDIASDK_EXPORT SampleFmts();int64_t MEDIASDK_EXPORT Time();
int64_t MEDIASDK_EXPORT NoPtsValue();
int64_t MEDIASDK_EXPORT ToTime(int64_t const& pts, Rational const& timebase);std::vector<std::string> MEDIASDK_EXPORT DisplayCardNames();
}
}
4.2.2 Utils实现
4.2.2.1 Report
void Report(bool on)
{if(on)av_log_set_callback(log_callback_help); elseav_log_set_callback(log_callback_null);
}
函数说明：
- 如果需要打印，设置一个可打印新的callback.
- 如果不要打印，设置一个不可打印的callback.
4.2.2.2 Formats
void Formats()
{AVInputFormat *ifmt = NULL;AVOutputFormat *ofmt = NULL;const char *last_name;printf("File formats:\n"" D. = Demuxing supported\n"" .E = Muxing supported\n"" --\n");last_name = "000";for (;;) {int decode = 0;int encode = 0;const char *name = NULL;const char *long_name = NULL;while ((ofmt = (AVOutputFormat *)av_oformat_next(ofmt))) {if ((name == NULL || strcmp(ofmt->name, name) < 0) &&strcmp(ofmt->name, last_name) > 0) {name = ofmt->name;long_name = ofmt->long_name;encode = 1;}}while ((ifmt = (AVInputFormat *)av_iformat_next(ifmt))) {if ((name == NULL || strcmp(ifmt->name, name) < 0) &&strcmp(ifmt->name, last_name) > 0) {name = ifmt->name;long_name = ifmt->long_name;encode = 0;}if (name && strcmp(ifmt->name, name) == 0)decode = 1;}if (name == NULL)break;last_name = name;printf(" %s%s %-15s %s\n",decode ? "D" : " ",encode ? "E" : " ",name,long_name ? long_name:" ");}
}
函数流程：
- 遍历输出格式和输入格式
- 打印名字和长名字
- 输入格式作为解复用(Demux)打印
- 输出格式作为复用（Mux）打印
4.2.2.3 Codecs
void Codecs(bool encoder)
{const AVCodecDescriptor **codecs;unsigned i, nb_codecs = get_codecs_sorted(&codecs);printf("%s:\n"" V..... = Video\n"" A..... = Audio\n"" S..... = Subtitle\n"" .F.... = Frame-level multithreading\n"" ..S... = Slice-level multithreading\n"" ...X.. = Codec is experimental\n"" ....B. = Supports draw_horiz_band\n"" .....D = Supports direct rendering method 1\n"" ------\n",encoder ? "Encoders" : "Decoders");for (i = 0; i < nb_codecs; i++) {const AVCodecDescriptor *desc = codecs[i];const AVCodec *codec = NULL;while ((codec = next_codec_for_id(desc->id, codec, encoder))) {printf(" %c", get_media_type_char(desc->type));printf((codec->capabilities & AV_CODEC_CAP_FRAME_THREADS) ? "F" : ".");printf((codec->capabilities & AV_CODEC_CAP_SLICE_THREADS) ? "S" : ".");printf((codec->capabilities & AV_CODEC_CAP_EXPERIMENTAL) ? "X" : ".");printf((codec->capabilities & AV_CODEC_CAP_DRAW_HORIZ_BAND)?"B" : ".");printf((codec->capabilities & AV_CODEC_CAP_DR1) ? "D" : ".");printf(" %-20s %s", codec->name, codec->long_name ? codec->long_name : "");if (strcmp(codec->name, desc->name))printf(" (codec %s)", desc->name);printf("\n");}}av_free(codecs);
}
函数流程：
- 遍历支持的编解码器
- 按照视频，音频，字幕，帧级多线程，切片级多线程，实验性，支持画横条，支持直接渲染等格式打印
4.2.2.4 Bsfs
void Bsfs()
{const AVBitStreamFilter *bsf = 0;void *opaque = NULL;printf("Bitstream filters:\n");while ((bsf = av_bsf_iterate(&opaque)))printf("%s\n", bsf->name);printf("\n");
}
函数流程：
- 遍历支持的Bitstream过滤器
- 打印过滤器名称
4.2.2.5 Protocols
void Protocols()
{void *opaque = NULL;const char *name;printf("Supported file protocols:\n""Input:\n");while ((name = avio_enum_protocols(&opaque, 0)))printf("%s\n", name);printf("Output:\n");while ((name = avio_enum_protocols(&opaque, 1)))printf("%s\n", name);
}
函数流程：
- 遍历支持的输入/输出协议
- 打印协议名称
4.2.2.6 Filters
void Filters()
{const AVFilter *filter = NULL;char descr[64], *descr_cur;void *opaque = NULL;int i, j;const AVFilterPad *pad;printf("Filters:\n"" T.. = Timeline support\n"" .S. = Slice threading\n"" ..C = Command support\n"" A = Audio input/output\n"" V = Video input/output\n"" N = Dynamic number and/or type of input/output\n"" | = Source or sink filter\n");while ((filter = av_filter_iterate(&opaque))) {descr_cur = descr;for (i = 0; i < 2; i++) {if (i) {*(descr_cur++) = '-';*(descr_cur++) = '>';}pad = i ? filter->outputs : filter->inputs;for (j = 0; pad && avfilter_pad_get_name(pad, j); j++) {if (descr_cur >= descr + sizeof(descr) - 4)break;*(descr_cur++) = get_media_type_char(avfilter_pad_get_type(pad, j));}if (!j)*(descr_cur++) = ((!i && (filter->flags & AVFILTER_FLAG_DYNAMIC_INPUTS)) ||( i && (filter->flags & AVFILTER_FLAG_DYNAMIC_OUTPUTS))) ? 'N' : '|';}*descr_cur = 0;printf(" %c%c%c %-17s %-10s %s\n",filter->flags & AVFILTER_FLAG_SUPPORT_TIMELINE ? 'T' : '.',filter->flags & AVFILTER_FLAG_SLICE_THREADS ? 'S' : '.',filter->process_command ? 'C' : '.',filter->name, descr, filter->description);}
}
函数流程：
- 遍历支持的过滤器
- 按照时间线，切片线程，命令支持，音频输入/输出，视频输入/输出和源/显示类型打印。
4.2.2.7 PixFmts
void PixFmts()
{const AVPixFmtDescriptor *pix_desc = NULL;printf("Pixel formats:\n""I.... = Supported Input format for conversion\n"".O... = Supported Output format for conversion\n""..H.. = Hardware accelerated format\n""...P. = Paletted format\n""....B = Bitstream format\n""FLAGS NAME NB_COMPONENTS BITS_PER_PIXEL\n""-----\n");#if !CONFIG_SWSCALE
# define sws_isSupportedInput(x) 0
# define sws_isSupportedOutput(x) 0
#endifwhile ((pix_desc = av_pix_fmt_desc_next(pix_desc))) {enum AVPixelFormat av_unused pix_fmt = av_pix_fmt_desc_get_id(pix_desc);printf("%c%c%c%c%c %-16s %d %2d\n",sws_isSupportedInput (pix_fmt) ? 'I' : '.',sws_isSupportedOutput(pix_fmt) ? 'O' : '.',pix_desc->flags & AV_PIX_FMT_FLAG_HWACCEL ? 'H' : '.',pix_desc->flags & AV_PIX_FMT_FLAG_PAL ? 'P' : '.',pix_desc->flags & AV_PIX_FMT_FLAG_BITSTREAM ? 'B' : '.',pix_desc->name,pix_desc->nb_components,av_get_bits_per_pixel(pix_desc));}
}
函数流程：
- 遍历支持的像素格式
- 按照输入，输出，硬件支持，调色板和位流类型打印。
4.2.2.8 SampleFmts
void SampleFmts()
{int i;char fmt_str[128];for (i = -1; i < AV_SAMPLE_FMT_NB; i++)printf("%s\n", av_get_sample_fmt_string(fmt_str, sizeof(fmt_str), (enum AVSampleFormat)i));
}
函数流程：
- 遍历支持的音频采样格式
- 打印音频采样格式
4.2.2.9 Time
int64_t Time()
{return av_gettime();
}
4.2.2.10 NoPtsValue
int64_t NoPtsValue()
{return AV_NOPTS_VALUE;
}
函数说明：
- 返回无效时间戳
4.2.2.11 ToTime
int64_t ToTime(int64_t const& pts, Rational const& timebase)
{AVRational tb1 = {timebase.num, timebase.den};AVRational tb2 = {1, AV_TIME_BASE};return av_rescale_q(pts, tb1, tb2);
}
函数说明：
- 将以1/AV_TIME_BASE秒为单位的时间戳转换位以timebase为单位的时间戳
- AV_TIME_BASE值为1000000
4.2.2.12 DisplayCardNames
std::vector<std::string> DisplayCardNames()
{std::vector<std::string> displayNames;IDXGIFactory * pFactory;HRESULT hr = CreateDXGIFactory(__uuidof(IDXGIFactory), (void**)(&pFactory));if(FAILED(hr))return displayNames;IDXGIAdapter * pAdapter;int iAdapterNum = 0;while(pFactory->EnumAdapters(iAdapterNum, &pAdapter) != DXGI_ERROR_NOT_FOUND){DXGI_ADAPTER_DESC desc;pAdapter->GetDesc(&desc);std::wstring aa(desc.Description);displayNames.push_back(WStringToString(aa));++iAdapterNum;}return displayNames;
}
函数流程：
- 遍历系统中显卡名称
- 将显卡名称放入数组并返回
示例
namespace mediasdk = media::sdk;
int main(int argc, char* argv[])
{mediasdk::Init();mediasdk::Formats();//打印支持的文件格式(封包格式).mediasdk::Codecs(true);//打印支持编码器.mediasdk::Codecs(false);//打印支持的解码器.mediasdk::Protocols();//打印支持的协议.mediasdk::Filters();//打印支持过滤器.mediasdk::PixFmts();//打印支持像素格式.mediasdk::SampleFmts();//打印支持采样格式.std::vector<std::string> names = media::sdk::DisplayCardNames();for(name: names)std::cout << "Display card: " << name << std::endl;return 0;
}
未完待续…