32 .net core获取ffmpeg转码进度及剩余时间 - xiaoxin01/Blog GitHub Wiki
ffmpeg虽然可以转码，但是从默认的输出信息无法看出转码进度及剩余时间
ffmpeg 转码的过程中输出的信息，无法直接获取当前转码的进度，一个示例的输出如下：
frame= 1777 fps=108 q=40.0 Lsize= 1954kB time=00:04:55.89 bitrate= 54.1kbits/s dup=0 drop=4141 speed=17.9x
frame=16788 fps=108 q=40.0 size= 1536kB time=00:04:39.38 bitrate= 45.0kbits/s dup=0 drop=3907 speed= 18x
从如上的输出信息可以发现，可以从两个方面获取进度：
- frame
- time
对应的进度计算公式如下：
- 1 - (total_frame - frame) / total_frame
- time / duration
可以通过ffprobe工具来获取视频信息
ffprobe -v quiet -print_format json -show_format -show_streams [video file]
输出的结果类似：
{
"streams": [
{
"index": 0,
"codec_name": "aac",
"codec_long_name": "AAC (Advanced Audio Coding)",
"profile": "LC",
"codec_type": "audio",
"codec_time_base": "1/44100",
"codec_tag_string": "mp4a",
"codec_tag": "0x6134706d",
"sample_fmt": "fltp",
"sample_rate": "44100",
"channels": 2,
"channel_layout": "stereo",
"bits_per_sample": 0,
"r_frame_rate": "0/0",
"avg_frame_rate": "0/0",
"time_base": "1/44100",
"start_pts": 0,
"start_time": "0.000000",
"duration_ts": 102390024,
"duration": "2321.769252",
"bit_rate": "141914",
"max_bit_rate": "236004",
"nb_frames": "100088",
"disposition": {
"default": 1,
"dub": 0,
"original": 0,
"comment": 0,
"lyrics": 0,
"karaoke": 0,
"forced": 0,
"hearing_impaired": 0,
"visual_impaired": 0,
"clean_effects": 0,
"attached_pic": 0,
"timed_thumbnails": 0
},
"tags": {
"creation_time": "2018-04-25T11:29:17.000000Z",
"language": "eng",
"handler_name": "Mainconcept MP4 Sound Media Handler"
}
},
{
"index": 1,
"codec_name": "h264",
"codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
"profile": "High",
"codec_type": "video",
"codec_time_base": "46480601/1859160000",
"codec_tag_string": "avc1",
"codec_tag": "0x31637661",
"width": 1364,
"height": 768,
"coded_width": 1376,
"coded_height": 768,
"has_b_frames": 1,
"sample_aspect_ratio": "1024:1023",
"display_aspect_ratio": "16:9",
"pix_fmt": "yuv420p",
"level": 32,
"color_range": "tv",
"color_space": "bt709",
"color_transfer": "bt709",
"color_primaries": "bt709",
"chroma_location": "left",
"refs": 1,
"is_avc": "true",
"nal_length_size": "4",
"r_frame_rate": "20/1",
"avg_frame_rate": "929580000/46480601",
"time_base": "1/20000",
"start_pts": 1000,
"start_time": "0.050000",
"duration_ts": 46479000,
"duration": "2323.950000",
"bit_rate": "413761",
"bits_per_raw_sample": "8",
"nb_frames": "46479",
"disposition": {
"default": 1,
"dub": 0,
"original": 0,
"comment": 0,
"lyrics": 0,
"karaoke": 0,
"forced": 0,
"hearing_impaired": 0,
"visual_impaired": 0,
"clean_effects": 0,
"attached_pic": 0,
"timed_thumbnails": 0
},
"tags": {
"creation_time": "2018-04-25T11:29:17.000000Z",
"language": "eng",
"handler_name": "Mainconcept MP4 Video Media Handler",
"encoder": "AVC Coding"
}
}
],
"format": {
"filename": "3.mp4",
"nb_streams": 2,
"nb_programs": 0,
"format_name": "mov,mp4,m4a,3gp,3g2,mj2",
"format_long_name": "QuickTime / MOV",
"start_time": "0.000000",
"duration": "2323.950000",
"size": "162498216",
"bit_rate": "559386",
"probe_score": 100,
"tags": {
"major_brand": "mp42",
"minor_version": "0",
"compatible_brands": "isommp42",
"creation_time": "2018-04-25T11:29:16.000000Z"
}
}
}可以看到，获取总帧数和持续时间的 JSonPath 分别如下：
- $.streams[1].nb_frames
- $.format.duration
用JObject解析JSon示例代码如下：
var videoFormatObject = JObject.Parse(json);
var durationObject = videoFormatObject.SelectToken("$.format.duration");
var duration = durationObject.Value<double>();虽然从转码进度可以得出转码所需时间，但并不直观，如何直观的显示出剩余时间？
分析ffmpeg转码时的输出发现，可以从 time, speed, duration 这3个数据计算出转码剩余时间：
剩余时间 = (duration - timeTranscoded) / speed
代码示例如下：
var transcodeLog = "frame= 1777 fps=108 q=40.0 Lsize= 1954kB time=00:04:55.89 bitrate= 54.1kbits/s dup=0 drop=4141 speed=17.9x";
var match = Regex.Match(transcodeLog, "time=(\\S+)");
if (match.Success)
{
var timeTranscoded = TimeSpan.Parse(match.Groups[1].Value).TotalSeconds;
// Trim() remove space when speed= 18x
speed = Convert.ToDouble(Regex.Match(transcodeLog, "speed=(.+)x").Groups[1].Value.Trim());
Console.WriteLine($"Percentage: {(timeTranscoded / duration).ToString("p")}, Remaining time: {((duration - timeTranscoded) / speed).ToString("f1")}s");
}调用进程时，需要设定 StartInfo.Redirect... = true，并监听数据接收事件，示例代码如下：
string param = $"-y -i [input video] -vcodec libx264 -vf scale=1280:720 -r 6 -crf 40 -acodec aac -q:a 0.4 -ac 1 [output video]";
using (Process p = new Process())
{
p.StartInfo.FileName = "ffmpeg.exe";
p.StartInfo.Arguments = param;
p.StartInfo.UseShellExecute = false;
p.StartInfo.RedirectStandardOutput = true;
p.StartInfo.RedirectStandardError = true;
var output = new DataReceivedEventHandler((sender, e) =>
{
if (!String.IsNullOrEmpty(e.Data))
{
Console.WriteLine(e.Data);
}
});
p.OutputDataReceived += output;
p.ErrorDataReceived += output;
p.Start();
p.BeginOutputReadLine();
p.BeginErrorReadLine(); // ffmpeg的进度输出是通过 Error 管道
p.WaitForExit();
}完成之后的转码进度及剩余时间显示：
Percentage: 2.37 %, Remaining time: 21.7s
Percentage: 5.40 %, Remaining time: 18.1s
Percentage: 8.44 %, Remaining time: 16.6s
...
Percentage: 96.83 %, Remaining time: 0.5s
Percentage: 99.87 %, Remaining time: 0.0s
Percentage: 100.00 %, Remaining time: 0.0s