C# 使用FFmpeg增加/减少音频音量
我目前正在使用C#调用来调用FFmpeg API来处理视频和音频。我有以下代码从视频中提取音频并将其写入文件C# 使用FFmpeg增加/减少音频音量,c#,ffmpeg,volume,C#,Ffmpeg,Volume,我目前正在使用C#调用来调用FFmpeg API来处理视频和音频。我有以下代码从视频中提取音频并将其写入文件 while (ffmpeg.av_read_frame(formatContext, &packet) >= 0) { if (packet.stream_index == streamIndex) { while (packet.size > 0) { int frameDecoded;
while (ffmpeg.av_read_frame(formatContext, &packet) >= 0)
{
if (packet.stream_index == streamIndex)
{
while (packet.size > 0)
{
int frameDecoded;
int frameDecodedResult = ffmpeg.avcodec_decode_audio4(codecContext, frame, &frameDecoded, packet);
if (frameDecoded > 0 && frameDecodedResult >= 0)
{
//writeAudio.WriteFrame(frame);
packet.data += totalBytesDecoded;
packet.size -= totalBytesDecoded;
}
}
frameIndex++;
}
Avcodec.av_free_packet(&packet);
}
public unsafe class FilterVolume
{
#region Private Member Variables
private AVFilterGraph* m_filterGraph = null;
private AVFilterContext* m_aBufferSourceFilterContext = null;
private AVFilterContext* m_aBufferSinkFilterContext = null;
#endregion
#region Private Constant Member Variables
private const int EAGAIN = 11;
#endregion
public FilterVolume(AVCodecContext* codecContext, AVStream* stream, float volume)
{
CodecContext = codecContext;
Stream = stream;
Volume = volume;
Initialise();
}
public AVFrame* Adjust(AVFrame* frame)
{
AVFrame* returnFilteredFrame = ffmpeg.av_frame_alloc();
if (m_aBufferSourceFilterContext != null && m_aBufferSinkFilterContext != null)
{
int bufferSourceAddFrameResult = ffmpeg.av_buffersrc_add_frame(m_aBufferSourceFilterContext, frame);
if (bufferSourceAddFrameResult < 0)
{
}
int bufferSinkGetFrameResult = ffmpeg.av_buffersink_get_frame(m_aBufferSinkFilterContext, returnFilteredFrame);
if (bufferSinkGetFrameResult < 0 && bufferSinkGetFrameResult != -EAGAIN)
{
}
}
return returnFilteredFrame;
}
public void Dispose()
{
Cleanup(m_filterGraph);
}
#region Private Properties
private AVCodecContext* CodecContext { get; set; }
private AVStream* Stream { get; set; }
private float Volume { get; set; }
#endregion
#region Private Setup Helper Functions
private void Initialise()
{
m_filterGraph = GetAllocatedFilterGraph();
string aBufferFilterArguments = string.Format("sample_fmt={0}:channel_layout={1}:sample_rate={2}:time_base={3}/{4}",
(int)CodecContext->sample_fmt,
CodecContext->channel_layout,
CodecContext->sample_rate,
Stream->time_base.num,
Stream->time_base.den);
AVFilterContext* aBufferSourceFilterContext = CreateFilter("abuffer", m_filterGraph, aBufferFilterArguments);
AVFilterContext* volumeFilterContext = CreateFilter("volume", m_filterGraph, string.Format("volume={0}", Volume));
AVFilterContext* aBufferSinkFilterContext = CreateFilter("abuffersink", m_filterGraph);
LinkFilter(aBufferSourceFilterContext, volumeFilterContext);
LinkFilter(volumeFilterContext, aBufferSinkFilterContext);
SetFilterGraphConfiguration(m_filterGraph, null);
m_aBufferSourceFilterContext = aBufferSourceFilterContext;
m_aBufferSinkFilterContext = aBufferSinkFilterContext;
}
#endregion
#region Private Cleanup Helper Functions
private static void Cleanup(AVFilterGraph* filterGraph)
{
if (filterGraph != null)
{
ffmpeg.avfilter_graph_free(&filterGraph);
}
}
#endregion
#region Provate Helpers
private AVFilterGraph* GetAllocatedFilterGraph()
{
AVFilterGraph* filterGraph = ffmpeg.avfilter_graph_alloc();
if (filterGraph == null)
{
}
return filterGraph;
}
private AVFilter* GetFilterByName(string name)
{
AVFilter* filter = ffmpeg.avfilter_get_by_name(name);
if (filter == null)
{
}
return filter;
}
private void SetFilterGraphConfiguration(AVFilterGraph* filterGraph, void* logContext)
{
int filterGraphConfigResult = ffmpeg.avfilter_graph_config(filterGraph, logContext);
if (filterGraphConfigResult < 0)
{
}
}
private AVFilterContext* CreateFilter(string filterName, AVFilterGraph* filterGraph, string filterArguments = null)
{
AVFilter* filter = GetFilterByName(filterName);
AVFilterContext* filterContext;
int aBufferFilterCreateResult = ffmpeg.avfilter_graph_create_filter(&filterContext, filter, filterName, filterArguments, null, filterGraph);
if (aBufferFilterCreateResult < 0)
{
}
return filterContext;
}
private void LinkFilter(AVFilterContext* source, AVFilterContext* destination)
{
int filterLinkResult = ffmpeg.avfilter_link(source, 0, destination, 0);
if (filterLinkResult < 0)
{
}
}
#endregion
}
string aBufferFilterArguments = string.Format("sample_fmt={0}:channel_layout=0x{1}:sample_rate={2}:time_base={3}/{4}",
(int)CodecContext->sample_fmt,
CodecContext->channel_layout,
CodecContext->sample_rate,
Stream->time_base.num,
Stream->time_base.den);
我不知道您使用的是什么API，但ffmpeg有一个命令，允许增加或减少音频： 减至一半：
ffmpeg -i input.wav -af "volume=0.5" output.wav
ffmpeg -i input.wav -af "volume=1.5" output.wav
ffmpeg -i input.wav -af "volume=10dB" output.wav
希望它能帮助您您需要做的是构建一个过滤图并通过该图处理音频流。在您的例子中，图形只是输入（“abuffer”）->VOLUME->OUTPUT（“abuffersink”）。 下面是一个示例控制台应用程序，演示了这一点。它松散地基于ffmpeg样本，并且 您可以这样使用它：
ChangeVolume.exe http://www.quirksmode.org/html5/videos/big_buck_bunny.mp4 bunny_half.mp4 0.5
class Program
{
static unsafe void Main(string[] args)
{
Console.WriteLine(@"Current directory: " + Environment.CurrentDirectory);
Console.WriteLine(@"Running in {0}-bit mode.", Environment.Is64BitProcess ? @"64" : @"32");
// adapt this to your context
var ffmpegPath = string.Format(@"../../../FFmpeg/bin/{0}", Environment.Is64BitProcess ? @"x64" : @"x86");
InteropHelper.SetDllDirectory(ffmpegPath);
int ret, i;
if (args.Length < 3)
{
Console.WriteLine("usage: ChangeVolume input output <volume ratio>");
return;
}
string in_filename = args[0];
string out_filename = args[1];
double ratio = double.Parse(args[2]);
ffmpeg.av_register_all();
ffmpeg.avfilter_register_all();
// open input file
AVFormatContext* ifmt_ctx = null;
InteropHelper.Check(ffmpeg.avformat_open_input(&ifmt_ctx, in_filename, null, null));
// dump input
ffmpeg.av_dump_format(ifmt_ctx, 0, in_filename, 0);
// get streams info to determine audio stream index
InteropHelper.Check(ffmpeg.avformat_find_stream_info(ifmt_ctx, null));
// determine input decoder
AVCodec* dec;
int audio_stream_index = ffmpeg.av_find_best_stream(ifmt_ctx, AVMediaType.AVMEDIA_TYPE_AUDIO, -1, -1, &dec, 0);
AVCodecContext* dec_ctx = ifmt_ctx->streams[audio_stream_index]->codec;
// open input decoder
InteropHelper.Check(ffmpeg.avcodec_open2(dec_ctx, dec, null));
// build a filter graph
AVFilterContext* buffersrc_ctx;
AVFilterContext* buffersink_ctx;
AVFilterGraph* filter_graph = init_filter_graph(ifmt_ctx, dec_ctx, audio_stream_index, &buffersrc_ctx, &buffersink_ctx, ratio);
// prepare output
AVFormatContext* ofmt_ctx = null;
InteropHelper.Check(ffmpeg.avformat_alloc_output_context2(&ofmt_ctx, null, null, out_filename));
InteropHelper.Check(ofmt_ctx);
// create output streams
AVCodecContext* enc_ctx = null;
ofmt_ctx->oformat->flags |= InteropHelper.AVFMT_NOTIMESTAMPS;
for (i = 0; i < ifmt_ctx->nb_streams; i++)
{
AVStream* in_stream = ifmt_ctx->streams[i];
if (in_stream->codec->codec_type == AVMediaType.AVMEDIA_TYPE_DATA) // skip these
continue;
AVStream* out_stream = ffmpeg.avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
InteropHelper.Check(out_stream);
InteropHelper.Check(ffmpeg.avcodec_copy_context(out_stream->codec, in_stream->codec));
out_stream->codec->codec_tag = 0;
if ((ofmt_ctx->oformat->flags & InteropHelper.AVFMT_GLOBALHEADER) != 0)
{
out_stream->codec->flags |= InteropHelper.AV_CODEC_FLAG_GLOBAL_HEADER;
}
if (i == audio_stream_index)
{
// create audio encoder from audio decoder
AVCodec* enc = ffmpeg.avcodec_find_encoder(dec_ctx->codec_id);
InteropHelper.Check(enc);
enc_ctx = ffmpeg.avcodec_alloc_context3(enc);
InteropHelper.Check(enc_ctx);
enc_ctx->sample_rate = dec_ctx->sample_rate;
enc_ctx->channel_layout = dec_ctx->channel_layout;
enc_ctx->channels = ffmpeg.av_get_channel_layout_nb_channels(enc_ctx->channel_layout);
enc_ctx->sample_fmt = enc->sample_fmts[0];
enc_ctx->time_base.num = 1;
enc_ctx->time_base.den = enc_ctx->sample_rate;
InteropHelper.Check(ffmpeg.avcodec_open2(enc_ctx, enc, null));
}
}
// dump output
ffmpeg.av_dump_format(ofmt_ctx, 0, out_filename, 1);
if ((ofmt_ctx->oformat->flags & InteropHelper.AVFMT_NOFILE) == 0)
{
// open output file
InteropHelper.Check(ffmpeg.avio_open(&ofmt_ctx->pb, out_filename, InteropHelper.AVIO_FLAG_WRITE));
}
// write output file header
InteropHelper.Check(ffmpeg.avformat_write_header(ofmt_ctx, null));
// read all packets and process
AVFrame* frame = ffmpeg.av_frame_alloc();
AVFrame* filt_frame = ffmpeg.av_frame_alloc();
while (true)
{
AVStream* in_stream;
AVStream* out_stream;
AVPacket pkt;
ret = ffmpeg.av_read_frame(ifmt_ctx, &pkt);
if (ret < 0)
break;
in_stream = ifmt_ctx->streams[pkt.stream_index];
if (in_stream->codec->codec_type == AVMediaType.AVMEDIA_TYPE_DATA)
continue;
// audio stream? we need to pass it through our filter graph
if (pkt.stream_index == audio_stream_index)
{
// decode audio (packet -> frame)
int got_frame = 0;
InteropHelper.Check(ffmpeg.avcodec_decode_audio4(dec_ctx, frame, &got_frame, &pkt));
if (got_frame > 0)
{
// add the frame into the filter graph
InteropHelper.Check(ffmpeg.av_buffersrc_add_frame(buffersrc_ctx, frame));
while (true)
{
// get the frame out from the filter graph
ret = ffmpeg.av_buffersink_get_frame(buffersink_ctx, filt_frame);
const int EAGAIN = 11;
if (ret == -EAGAIN)
break;
InteropHelper.Check(ret);
// encode audio (frame -> packet)
AVPacket enc_pkt = new AVPacket();
int got_packet = 0;
InteropHelper.Check(ffmpeg.avcodec_encode_audio2(enc_ctx, &enc_pkt, filt_frame, &got_packet));
enc_pkt.stream_index = pkt.stream_index;
InteropHelper.Check(ffmpeg.av_interleaved_write_frame(ofmt_ctx, &enc_pkt));
ffmpeg.av_frame_unref(filt_frame);
}
}
}
else
{
// write other (video) streams
out_stream = ofmt_ctx->streams[pkt.stream_index];
pkt.pts = ffmpeg.av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, AVRounding.AV_ROUND_NEAR_INF | AVRounding.AV_ROUND_PASS_MINMAX);
pkt.dts = ffmpeg.av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, AVRounding.AV_ROUND_NEAR_INF | AVRounding.AV_ROUND_PASS_MINMAX);
pkt.duration = ffmpeg.av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
pkt.pos = -1;
InteropHelper.Check(ffmpeg.av_interleaved_write_frame(ofmt_ctx, &pkt));
}
ffmpeg.av_packet_unref(&pkt);
}
// write trailer, close file
ffmpeg.av_write_trailer(ofmt_ctx);
ffmpeg.avformat_close_input(&ifmt_ctx);
if ((ofmt_ctx->oformat->flags & InteropHelper.AVFMT_NOFILE) == 0)
{
ffmpeg.avio_closep(&ofmt_ctx->pb);
}
ffmpeg.avformat_free_context(ofmt_ctx);
ffmpeg.av_frame_free(&filt_frame);
ffmpeg.av_frame_free(&frame);
ffmpeg.avfilter_graph_free(&filter_graph);
return;
}
static unsafe AVFilterGraph* init_filter_graph(AVFormatContext* format, AVCodecContext* codec, int audio_stream_index, AVFilterContext** buffersrc_ctx, AVFilterContext** buffersink_ctx, double volumeRatio)
{
// create graph
var filter_graph = ffmpeg.avfilter_graph_alloc();
InteropHelper.Check(filter_graph);
// add input filter
var abuffersrc = ffmpeg.avfilter_get_by_name("abuffer");
if (abuffersrc == null) InteropHelper.CheckTag("\x00F8FIL");
string args = string.Format("sample_fmt={0}:channel_layout={1}:sample_rate={2}:time_base={3}/{4}",
(int)codec->sample_fmt,
codec->channel_layout,
codec->sample_rate,
format->streams[audio_stream_index]->time_base.num,
format->streams[audio_stream_index]->time_base.den);
InteropHelper.Check(ffmpeg.avfilter_graph_create_filter(buffersrc_ctx, abuffersrc, "IN", args, null, filter_graph));
// add volume filter
var volume = ffmpeg.avfilter_get_by_name("volume");
if (volume == null) InteropHelper.CheckTag("\x00F8FIL");
AVFilterContext* volume_ctx;
InteropHelper.Check(ffmpeg.avfilter_graph_create_filter(&volume_ctx, volume, "VOL", "volume=" + volumeRatio.ToString(CultureInfo.InvariantCulture), null, filter_graph));
// add output filter
var abuffersink = ffmpeg.avfilter_get_by_name("abuffersink");
if (abuffersink == null) InteropHelper.CheckTag("\x00F8FIL");
InteropHelper.Check(ffmpeg.avfilter_graph_create_filter(buffersink_ctx, abuffersink, "OUT", "", null, filter_graph));
// connect input -> volume -> output
InteropHelper.Check(ffmpeg.avfilter_link(*buffersrc_ctx, 0, volume_ctx, 0));
InteropHelper.Check(ffmpeg.avfilter_link(volume_ctx, 0, *buffersink_ctx, 0));
InteropHelper.Check(ffmpeg.avfilter_graph_config(filter_graph, null));
return filter_graph;
}
}
类程序
{
静态不安全void Main（字符串[]args）
{
Console.WriteLine（@“当前目录：”+Environment.CurrentDirectory）；
Console.WriteLine（@“在{0}-位模式下运行”，Environment.Is64BitProcess？@“64”：@“32”）；
//根据您的环境调整此选项
var ffmpegPath=string.Format（@./../../../FFmpeg/bin/{0}），Environment.is64位进程？@“x64”：@“x86”）；
InteropHelper.SetDllDirectory（ffmpegPath）；
int ret，i；
如果（参数长度<3）
{
Console.WriteLine（“用法：ChangeVolume输入输出”）；
返回；
}
_filename=args[0]中的字符串；
字符串输出_filename=args[1]；
double ratio=double.Parse（args[2]）；
ffmpeg.av_register_all（）；
ffmpeg.avfilter_register_all（）；
//打开输入文件
AVFormatContext*ifmt_ctx=null；
InteropHelper.Check（ffmpeg.avformat_open_input（&ifmt_ctx，in_filename，null，null））；
//转储输入
av_dump_格式（ifmt_ctx，0，in_文件名，0）；
//获取流信息以确定音频流索引
InteropHelper.Check（ffmpeg.avformat_find_stream_info（ifmt_ctx，null））；
//确定输入解码器
AVCodec*dec；
int audio\u stream\u index=ffmpeg.av\u find\u best\u stream（ifmt\u ctx、AVMediaType.AVMEDIA\u TYPE\u audio、-1、&dec，0）；
AVCodecContext*dec_ctx=ifmt_ctx->streams[audio_stream_index]->编解码器；
//开放输入解码器
InteropHelper.Check（ffmpeg.avcodec_open2（dec_ctx，dec，null））；
//构建一个过滤图
AVFilterContext*缓冲区src_ctx；
AVFilterContext*buffersink_ctx；
AVFilterGraph*filter\u graph=init\u filter\u graph（ifmt\u ctx、dec\u ctx、音频流索引、缓冲区src\u ctx、缓冲区sink\u ctx、比率）；
//准备输出
AVFormatContext*ofmt_ctx=null；
InteropHelper.Check（ffmpeg.avformat_alloc_output_context2（&ofmt_ctx，null，null，out_filename））；
检查（ofmt_ctx）；
//创建输出流
AVCodecContext*enc_ctx=null；
ofmt_ctx->oformat->flags |=InteropHelper.AVFMT_NOTIMESTAMPS；
对于（i=0；inb\u streams；i++）
{
AVStream*in_stream=ifmt_ctx->streams[i]；
如果（在\u流->编解码器->编解码器\u类型==AVMediaType.AVMEDIA\u类型\u数据中）//跳过这些
继续；
AVStream*out\u stream=ffmpeg.avformat\u new\u stream（ofmt\u ctx，in\u stream->codec->codec）；
InteropHelper.Check（out_流）；
InteropHelper.Check（ffmpeg.avcodec\u copy\u上下文（out\u stream->codec，in\u stream->codec））；
out\u stream->codec->codec\u tag=0；
if（（ofmt_ctx->oformat->flags&InteropHelper.AVFMT_GLOBALHEADER）！=0）
{
out_stream->codec->flags |=InteropHelper.AV_codec_FLAG_GLOBAL_头；
}
if（i==音频流索引）
{
//从音频解码器创建音频编码器
AVCodec*enc=ffmpeg.AVCodec\u find\u编码器（dec\u ctx->codec\u id）；
互通检查（enc）；
enc_ctx=ffmpeg.avcodec_alloc_context3（enc）；
互通检查（enc_ctx）；
enc_ctx->采样率=dec_ctx->采样率；
enc_ctx->channel_layout=dec_ctx->channel_layout；
enc\u ctx->channels=ffmpeg.av\u get\u channel\u layout\u nb\u channels（enc\u ctx->channel\u layout）；
enc_ctx->sample_fmt=enc->sample_fmts[0]；
enc_ctx->time_base.num=1；
enc\u ctx->time\u base.den=enc\u ctx->sample\u rate；
InteropHelper.Check（ffmpeg.avcodec_open2（enc_ctx，enc，null））；
}
}
//转储输出
av_dump_格式（ofmt_ctx，0，out_文件名，1）；
if（（ofmt_ctx->oformat->flags&InteropHelper.AVFMT_NOFILE）==0）
{
//打开输出文件
检查（ffmpeg.avio_open（&ofmt_ctx->pb，out_filename，InteropHelper.avio_FLAG_WRITE））；
}
//写入输出文件头
InteropHelper.Check（ffmpeg.avformat_write_头（ofmt_ctx，null））；
//读取所有数据包并进行处理
AVFrame*frame=ffmpeg.av_frame_alloc（）；
AVFrame*filt_frame=ffmpeg.av_frame_alloc（）；
while（true）
{
AVStream*在_流中；
AVStream*输出流；
AVPacket-pkt；
ret=ffmpeg.av\u read\u帧（ifmt\u ctx和pkt）；
如果（ret<0）
打破
in_stream=ifmt_ctx->streams[pkt.stream_index]；
如果（在溪流中）->cod
class Program
{
static unsafe void Main(string[] args)
{
Console.WriteLine(@"Current directory: " + Environment.CurrentDirectory);
Console.WriteLine(@"Running in {0}-bit mode.", Environment.Is64BitProcess ? @"64" : @"32");
// adapt this to your context
var ffmpegPath = string.Format(@"../../../FFmpeg/bin/{0}", Environment.Is64BitProcess ? @"x64" : @"x86");
InteropHelper.SetDllDirectory(ffmpegPath);
int ret, i;
if (args.Length < 3)
{
Console.WriteLine("usage: ChangeVolume input output <volume ratio>");
return;
}
string in_filename = args[0];
string out_filename = args[1];
double ratio = double.Parse(args[2]);
ffmpeg.av_register_all();
ffmpeg.avfilter_register_all();
// open input file
AVFormatContext* ifmt_ctx = null;
InteropHelper.Check(ffmpeg.avformat_open_input(&ifmt_ctx, in_filename, null, null));
// dump input
ffmpeg.av_dump_format(ifmt_ctx, 0, in_filename, 0);
// get streams info to determine audio stream index
InteropHelper.Check(ffmpeg.avformat_find_stream_info(ifmt_ctx, null));
// determine input decoder
AVCodec* dec;
int audio_stream_index = ffmpeg.av_find_best_stream(ifmt_ctx, AVMediaType.AVMEDIA_TYPE_AUDIO, -1, -1, &dec, 0);
AVCodecContext* dec_ctx = ifmt_ctx->streams[audio_stream_index]->codec;
// open input decoder
InteropHelper.Check(ffmpeg.avcodec_open2(dec_ctx, dec, null));
// build a filter graph
AVFilterContext* buffersrc_ctx;
AVFilterContext* buffersink_ctx;
AVFilterGraph* filter_graph = init_filter_graph(ifmt_ctx, dec_ctx, audio_stream_index, &buffersrc_ctx, &buffersink_ctx, ratio);
// prepare output
AVFormatContext* ofmt_ctx = null;
InteropHelper.Check(ffmpeg.avformat_alloc_output_context2(&ofmt_ctx, null, null, out_filename));
InteropHelper.Check(ofmt_ctx);
// create output streams
AVCodecContext* enc_ctx = null;
ofmt_ctx->oformat->flags |= InteropHelper.AVFMT_NOTIMESTAMPS;
for (i = 0; i < ifmt_ctx->nb_streams; i++)
{
AVStream* in_stream = ifmt_ctx->streams[i];
if (in_stream->codec->codec_type == AVMediaType.AVMEDIA_TYPE_DATA) // skip these
continue;
AVStream* out_stream = ffmpeg.avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
InteropHelper.Check(out_stream);
InteropHelper.Check(ffmpeg.avcodec_copy_context(out_stream->codec, in_stream->codec));
out_stream->codec->codec_tag = 0;
if ((ofmt_ctx->oformat->flags & InteropHelper.AVFMT_GLOBALHEADER) != 0)
{
out_stream->codec->flags |= InteropHelper.AV_CODEC_FLAG_GLOBAL_HEADER;
}
if (i == audio_stream_index)
{
// create audio encoder from audio decoder
AVCodec* enc = ffmpeg.avcodec_find_encoder(dec_ctx->codec_id);
InteropHelper.Check(enc);
enc_ctx = ffmpeg.avcodec_alloc_context3(enc);
InteropHelper.Check(enc_ctx);
enc_ctx->sample_rate = dec_ctx->sample_rate;
enc_ctx->channel_layout = dec_ctx->channel_layout;
enc_ctx->channels = ffmpeg.av_get_channel_layout_nb_channels(enc_ctx->channel_layout);
enc_ctx->sample_fmt = enc->sample_fmts[0];
enc_ctx->time_base.num = 1;
enc_ctx->time_base.den = enc_ctx->sample_rate;
InteropHelper.Check(ffmpeg.avcodec_open2(enc_ctx, enc, null));
}
}
// dump output
ffmpeg.av_dump_format(ofmt_ctx, 0, out_filename, 1);
if ((ofmt_ctx->oformat->flags & InteropHelper.AVFMT_NOFILE) == 0)
{
// open output file
InteropHelper.Check(ffmpeg.avio_open(&ofmt_ctx->pb, out_filename, InteropHelper.AVIO_FLAG_WRITE));
}
// write output file header
InteropHelper.Check(ffmpeg.avformat_write_header(ofmt_ctx, null));
// read all packets and process
AVFrame* frame = ffmpeg.av_frame_alloc();
AVFrame* filt_frame = ffmpeg.av_frame_alloc();
while (true)
{
AVStream* in_stream;
AVStream* out_stream;
AVPacket pkt;
ret = ffmpeg.av_read_frame(ifmt_ctx, &pkt);
if (ret < 0)
break;
in_stream = ifmt_ctx->streams[pkt.stream_index];
if (in_stream->codec->codec_type == AVMediaType.AVMEDIA_TYPE_DATA)
continue;
// audio stream? we need to pass it through our filter graph
if (pkt.stream_index == audio_stream_index)
{
// decode audio (packet -> frame)
int got_frame = 0;
InteropHelper.Check(ffmpeg.avcodec_decode_audio4(dec_ctx, frame, &got_frame, &pkt));
if (got_frame > 0)
{
// add the frame into the filter graph
InteropHelper.Check(ffmpeg.av_buffersrc_add_frame(buffersrc_ctx, frame));
while (true)
{
// get the frame out from the filter graph
ret = ffmpeg.av_buffersink_get_frame(buffersink_ctx, filt_frame);
const int EAGAIN = 11;
if (ret == -EAGAIN)
break;
InteropHelper.Check(ret);
// encode audio (frame -> packet)
AVPacket enc_pkt = new AVPacket();
int got_packet = 0;
InteropHelper.Check(ffmpeg.avcodec_encode_audio2(enc_ctx, &enc_pkt, filt_frame, &got_packet));
enc_pkt.stream_index = pkt.stream_index;
InteropHelper.Check(ffmpeg.av_interleaved_write_frame(ofmt_ctx, &enc_pkt));
ffmpeg.av_frame_unref(filt_frame);
}
}
}
else
{
// write other (video) streams
out_stream = ofmt_ctx->streams[pkt.stream_index];
pkt.pts = ffmpeg.av_rescale_q_rnd(pkt.pts, in_stream->time_base, out_stream->time_base, AVRounding.AV_ROUND_NEAR_INF | AVRounding.AV_ROUND_PASS_MINMAX);
pkt.dts = ffmpeg.av_rescale_q_rnd(pkt.dts, in_stream->time_base, out_stream->time_base, AVRounding.AV_ROUND_NEAR_INF | AVRounding.AV_ROUND_PASS_MINMAX);
pkt.duration = ffmpeg.av_rescale_q(pkt.duration, in_stream->time_base, out_stream->time_base);
pkt.pos = -1;
InteropHelper.Check(ffmpeg.av_interleaved_write_frame(ofmt_ctx, &pkt));
}
ffmpeg.av_packet_unref(&pkt);
}
// write trailer, close file
ffmpeg.av_write_trailer(ofmt_ctx);
ffmpeg.avformat_close_input(&ifmt_ctx);
if ((ofmt_ctx->oformat->flags & InteropHelper.AVFMT_NOFILE) == 0)
{
ffmpeg.avio_closep(&ofmt_ctx->pb);
}
ffmpeg.avformat_free_context(ofmt_ctx);
ffmpeg.av_frame_free(&filt_frame);
ffmpeg.av_frame_free(&frame);
ffmpeg.avfilter_graph_free(&filter_graph);
return;
}
static unsafe AVFilterGraph* init_filter_graph(AVFormatContext* format, AVCodecContext* codec, int audio_stream_index, AVFilterContext** buffersrc_ctx, AVFilterContext** buffersink_ctx, double volumeRatio)
{
// create graph
var filter_graph = ffmpeg.avfilter_graph_alloc();
InteropHelper.Check(filter_graph);
// add input filter
var abuffersrc = ffmpeg.avfilter_get_by_name("abuffer");
if (abuffersrc == null) InteropHelper.CheckTag("\x00F8FIL");
string args = string.Format("sample_fmt={0}:channel_layout={1}:sample_rate={2}:time_base={3}/{4}",
(int)codec->sample_fmt,
codec->channel_layout,
codec->sample_rate,
format->streams[audio_stream_index]->time_base.num,
format->streams[audio_stream_index]->time_base.den);
InteropHelper.Check(ffmpeg.avfilter_graph_create_filter(buffersrc_ctx, abuffersrc, "IN", args, null, filter_graph));
// add volume filter
var volume = ffmpeg.avfilter_get_by_name("volume");
if (volume == null) InteropHelper.CheckTag("\x00F8FIL");
AVFilterContext* volume_ctx;
InteropHelper.Check(ffmpeg.avfilter_graph_create_filter(&volume_ctx, volume, "VOL", "volume=" + volumeRatio.ToString(CultureInfo.InvariantCulture), null, filter_graph));
// add output filter
var abuffersink = ffmpeg.avfilter_get_by_name("abuffersink");
if (abuffersink == null) InteropHelper.CheckTag("\x00F8FIL");
InteropHelper.Check(ffmpeg.avfilter_graph_create_filter(buffersink_ctx, abuffersink, "OUT", "", null, filter_graph));
// connect input -> volume -> output
InteropHelper.Check(ffmpeg.avfilter_link(*buffersrc_ctx, 0, volume_ctx, 0));
InteropHelper.Check(ffmpeg.avfilter_link(volume_ctx, 0, *buffersink_ctx, 0));
InteropHelper.Check(ffmpeg.avfilter_graph_config(filter_graph, null));
return filter_graph;
}
}
public class InteropHelper
{
[DllImport("kernel32", SetLastError = true)]
public static extern bool SetDllDirectory(string lpPathName);
public static readonly int AVERROR_EOF = -GetTag("EOF ");
public static readonly int AVERROR_UNKNOWN = -GetTag("UNKN");
public static readonly int AVFMT_GLOBALHEADER = 0x0040;
public static readonly int AVFMT_NOFILE = 0x0001;
public static readonly int AVIO_FLAG_WRITE = 2;
public static readonly int AV_CODEC_FLAG_GLOBAL_HEADER = (1 << 22);
public static readonly int AV_ROUND_ZERO = 0;
public static readonly int AV_ROUND_INF = 1;
public static readonly int AV_ROUND_DOWN = 2;
public static readonly int AV_ROUND_UP = 3;
public static readonly int AV_ROUND_PASS_MINMAX = 8192;
public static readonly int AV_ROUND_NEAR_INF = 5;
public static readonly int AVFMT_NOTIMESTAMPS = 0x0080;
public static unsafe void Check(void* ptr)
{
if (ptr != null)
return;
const int ENOMEM = 12;
Check(-ENOMEM);
}
public static unsafe void Check(IntPtr ptr)
{
if (ptr != IntPtr.Zero)
return;
Check((void*)null);
}
// example: "\x00F8FIL" is "Filter not found" (check libavutil/error.h)
public static void CheckTag(string tag)
{
Check(-GetTag(tag));
}
public static int GetTag(string tag)
{
var bytes = new byte[4];
for (int i = 0; i < 4; i++)
{
bytes[i] = (byte)tag[i];
}
return BitConverter.ToInt32(bytes, 0);
}
public static void Check(int res)
{
if (res >= 0)
return;
string err = "ffmpeg error " + res;
string text = GetErrorText(res);
if (!string.IsNullOrWhiteSpace(text))
{
err += ": " + text;
}
throw new Exception(err);
}
public static string GetErrorText(int res)
{
IntPtr err = Marshal.AllocHGlobal(256);
try
{
ffmpeg.av_strerror(res, err, 256);
return Marshal.PtrToStringAnsi(err);
}
finally
{
Marshal.FreeHGlobal(err);
}
}
}