最简单的基于FFMPEG的转码程序

Dear 丶 2022-08-20 05:26 123阅读 0赞

本文介绍一个简单的基于FFmpeg的转码器。它可以将一种视频格式（包括封转格式和编码格式）转换为另一种视频格式。转码器在视音频编解码处理的程序中，属于一个比较复杂的东西。因为它结合了视频的解码和编码。一个视频播放器，一般只包含解码功能；一个视频编码工具，一般只包含编码功能；而一个视频转码器，则需要先对视频进行解码，然后再对视频进行编码，因而相当于解码器和编码器的结合。下图例举了一个视频的转码流程。输入视频的封装格式是FLV，视频编码标准是H.264，音频编码标准是AAC；输出视频的封装格式是AVI，视频编码标准是MPEG2，音频编码标准是MP3。从流程中可以看出，首先从输入视频中分离出视频码流和音频压缩码流，然后分别将视频码流和音频码流进行解码，获取到非压缩的像素数据/音频采样数据，接着将非压缩的像素数据/音频采样数据重新进行编码，获得重新编码后的视频码流和音频码流，最后将视频码流和音频码流重新封装成一个文件。

![SouthEast][]

本文介绍的视频转码器正是使用FFMPEG类库从编程的角度实现了上述流程。该例子是从FFmpeg的例子改编的，平台是VC2010，类库版本是2014.5.6。

## 流程图（2014.9.29更新） ##

下面附两张使用FFmpeg转码视频的流程图。图中使用浅绿色标出了视频的编码、解码函数。从代码中可以看出，使用了AVFilter的不少东西，因此建议先学习AVFilter的内容后再看这个转码器的源代码。

PS：实际上，转码器不是一定依赖AVFilter的。因此打算有时间对这个转码器进行进一步的简化，使学习的人无需AVFilter的基础也可以理解转码器。

![SouthEast 1][]

简单介绍一下流程中各个函数的意义：  
open\_input\_file()：打开输入文件，并初始化相关的结构体。  
open\_output\_file()：打开输出文件，并初始化相关的结构体。  
init\_filters()：初始化AVFilter相关的结构体。  
av\_read\_frame()：从输入文件中读取一个AVPacket。  
avcodec\_decode\_video2()：解码一个视频AVPacket（存储H.264等压缩码流数据）为AVFrame（存储YUV等非压缩的像素数据）。  
avcodec\_decode\_video4()：解码一个音频AVPacket（存储MP3等压缩码流数据）为AVFrame（存储PCM采样数据）。  
filter\_encode\_write\_frame()：编码一个AVFrame。  
flush\_encoder()：输入文件读取完毕后，输出编码器中剩余的AVPacket。

以上函数中open\_input\_file()，open\_output\_file()，init\_filters()中的函数在其他文章中都有所叙述，在这里不再重复：

open\_input\_file()可参考：[100行代码实现最简单的基于FFMPEG+SDL的视频播放器（SDL1.x）][100_FFMPEG_SDL_SDL1.x]

open\_output\_file()可参考：[最简单的基于FFMPEG的视频编码器（YUV编码为H.264）][FFMPEG_YUV_H.264]

init\_filters()可参考：[最简单的基于FFmpeg的AVfilter例子（水印叠加）][FFmpeg_AVfilter]

在这里介绍一下其中编码的函数filter\_encode\_write\_frame()。filter\_encode\_write\_frame()函数的流程如下图所示，它完成了视频/音频的编码功能。

PS：视频和音频的编码流程中除了编码函数avcodec\_encode\_video2()和avcodec\_encode\_audio2()不一样之外，其他部分几乎完全一样。

![SouthEast 2][]

简单介绍一下filter\_encode\_write\_frame()中各个函数的意义：

av\_buffersrc\_add\_frame()：将解码后的AVFrame加入Filtergraph。

av\_buffersink\_get\_buffer\_ref()：从Filtergraph中取一个AVFrame。

avcodec\_encode\_video2()：编码一个视频AVFrame为AVPacket。

avcodec\_encode\_audio2()：编码一个音频AVFrame为AVPacket。

av\_interleaved\_write\_frame()：将编码后的AVPacket写入文件。

## 代码 ##

贴上代码

**\[cpp\]** [ view plain][view plain] [ copy][view plain]  [![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  /\*
2.   \*最简单的基于FFmpeg的转码器
3.   \*Simplest FFmpeg Transcoder
4.   \*
5.   \*雷霄骅 Lei Xiaohua
6.   \*leixiaohua1020@126.com
7.   \*中国传媒大学/数字电视技术
8.   \*Communication University of China / DigitalTV Technology
9.   \*http://blog.csdn.net/leixiaohua1020
10.  \*
11.  \*本程序实现了视频格式之间的转换。是一个最简单的视频转码程序。
12.  \*
13.  \*/
14. 
15. \#include "stdafx.h"
16. extern "C"
17. \{
18. \#include "libavcodec/avcodec.h"
19. \#include "libavformat/avformat.h"
20. \#include "libavfilter/avfiltergraph.h"
21. \#include "libavfilter/avcodec.h"
22. \#include "libavfilter/buffersink.h"
23. \#include "libavfilter/buffersrc.h"
24. \#include "libavutil/avutil.h"
25. \#include "libavutil/opt.h"
26. \#include "libavutil/pixdesc.h"
27. \};
28. 
29. 
30. 
31. static AVFormatContext \*ifmt\_ctx;
32. static AVFormatContext \*ofmt\_ctx;
33. typedef struct FilteringContext\{
34. AVFilterContext\*buffersink\_ctx;
35. AVFilterContext\*buffersrc\_ctx;
36. AVFilterGraph\*filter\_graph;
37. \} FilteringContext;
38. static FilteringContext \*filter\_ctx;
39. static int open\_input\_file(const char \*filename)
40. \{
41. int ret;
42. unsigned int i;
43. ifmt\_ctx =NULL;
44. if ((ret = avformat\_open\_input(&ifmt\_ctx,filename, NULL, NULL)) < 0) \{
45. av\_log(NULL, AV\_LOG\_ERROR, "Cannot openinput file\\n");
46. return ret;
47. \}
48. if ((ret = avformat\_find\_stream\_info(ifmt\_ctx, NULL))< 0) \{
49. av\_log(NULL, AV\_LOG\_ERROR, "Cannot findstream information\\n");
50. return ret;
51. \}
52. for (i = 0; i < ifmt\_ctx->nb\_streams; i++) \{
53. AVStream\*stream;
54. AVCodecContext \*codec\_ctx;
55. stream =ifmt\_ctx->streams\[i\];
56. codec\_ctx =stream->codec;
57. /\* Reencode video & audio and remux subtitles etc. \*/
58. if (codec\_ctx->codec\_type == AVMEDIA\_TYPE\_VIDEO
59. ||codec\_ctx->codec\_type == AVMEDIA\_TYPE\_AUDIO) \{
60. /\* Open decoder \*/
61. ret =avcodec\_open2(codec\_ctx,
62. avcodec\_find\_decoder(codec\_ctx->codec\_id), NULL);
63. if (ret < 0) \{
64. av\_log(NULL, AV\_LOG\_ERROR, "Failed toopen decoder for stream \#%u\\n", i);
65. return ret;
66. \}
67. \}
68. \}
69. av\_dump\_format(ifmt\_ctx, 0, filename, 0);
70. return 0;
71. \}
72. static int open\_output\_file(const char \*filename)
73. \{
74. AVStream\*out\_stream;
75. AVStream\*in\_stream;
76. AVCodecContext\*dec\_ctx, \*enc\_ctx;
77. AVCodec\*encoder;
78. int ret;
79. unsigned int i;
80. ofmt\_ctx =NULL;
81. avformat\_alloc\_output\_context2(&ofmt\_ctx, NULL, NULL, filename);
82. if (!ofmt\_ctx) \{
83. av\_log(NULL, AV\_LOG\_ERROR, "Could notcreate output context\\n");
84. return AVERROR\_UNKNOWN;
85. \}
86. for (i = 0; i < ifmt\_ctx->nb\_streams; i++) \{
87. out\_stream= avformat\_new\_stream(ofmt\_ctx, NULL);
88. if (!out\_stream) \{
89. av\_log(NULL, AV\_LOG\_ERROR, "Failedallocating output stream\\n");
90. return AVERROR\_UNKNOWN;
91. \}
92. in\_stream =ifmt\_ctx->streams\[i\];
93. dec\_ctx =in\_stream->codec;
94. enc\_ctx =out\_stream->codec;
95. if (dec\_ctx->codec\_type == AVMEDIA\_TYPE\_VIDEO
96. ||dec\_ctx->codec\_type == AVMEDIA\_TYPE\_AUDIO) \{
97. /\* in this example, we choose transcoding to same codec \*/
98. encoder= avcodec\_find\_encoder(dec\_ctx->codec\_id);
99. /\* In this example, we transcode to same properties(picture size,
100.  \* sample rate etc.). These properties can be changed for output
101.  \* streams easily using filters \*/
102. if (dec\_ctx->codec\_type == AVMEDIA\_TYPE\_VIDEO) \{
103. enc\_ctx->height = dec\_ctx->height;
104. enc\_ctx->width = dec\_ctx->width;
105. enc\_ctx->sample\_aspect\_ratio = dec\_ctx->sample\_aspect\_ratio;
106. /\* take first format from list of supported formats \*/
107. enc\_ctx->pix\_fmt = encoder->pix\_fmts\[0\];
108. /\* video time\_base can be set to whatever is handy andsupported by encoder \*/
109. enc\_ctx->time\_base = dec\_ctx->time\_base;
110. \} else \{
111. enc\_ctx->sample\_rate = dec\_ctx->sample\_rate;
112. enc\_ctx->channel\_layout = dec\_ctx->channel\_layout;
113. enc\_ctx->channels = av\_get\_channel\_layout\_nb\_channels(enc\_ctx->channel\_layout);
114. /\* take first format from list of supported formats \*/
115. enc\_ctx->sample\_fmt = encoder->sample\_fmts\[0\];
116. AVRationaltime\_base=\{1, enc\_ctx->sample\_rate\};
117. enc\_ctx->time\_base = time\_base;
118. \}
119. /\* Third parameter can be used to pass settings to encoder\*/
120. ret =avcodec\_open2(enc\_ctx, encoder, NULL);
121. if (ret < 0) \{
122. av\_log(NULL, AV\_LOG\_ERROR, "Cannot openvideo encoder for stream \#%u\\n", i);
123. return ret;
124. \}
125. \} else if(dec\_ctx->codec\_type == AVMEDIA\_TYPE\_UNKNOWN) \{
126. av\_log(NULL, AV\_LOG\_FATAL, "Elementarystream \#%d is of unknown type, cannot proceed\\n", i);
127. return AVERROR\_INVALIDDATA;
128. \} else \{
129. /\* if this stream must be remuxed \*/
130. ret =avcodec\_copy\_context(ofmt\_ctx->streams\[i\]->codec,
131. ifmt\_ctx->streams\[i\]->codec);
132. if (ret < 0) \{
133. av\_log(NULL, AV\_LOG\_ERROR, "Copyingstream context failed\\n");
134. return ret;
135. \}
136. \}
137. if (ofmt\_ctx->oformat->flags &AVFMT\_GLOBALHEADER)
138. enc\_ctx->flags |= CODEC\_FLAG\_GLOBAL\_HEADER;
139. \}
140. av\_dump\_format(ofmt\_ctx, 0, filename, 1);
141. if (!(ofmt\_ctx->oformat->flags &AVFMT\_NOFILE)) \{
142. ret =avio\_open(&ofmt\_ctx->pb, filename, AVIO\_FLAG\_WRITE);
143. if (ret < 0) \{
144. av\_log(NULL, AV\_LOG\_ERROR, "Could notopen output file '%s'", filename);
145. return ret;
146. \}
147. \}
148. /\* init muxer, write output file header \*/
149. ret =avformat\_write\_header(ofmt\_ctx, NULL);
150. if (ret < 0) \{
151. av\_log(NULL,AV\_LOG\_ERROR, "Error occurred when openingoutput file\\n");
152. return ret;
153. \}
154. return 0;
155. \}
156. static intinit\_filter(FilteringContext\* fctx, AVCodecContext \*dec\_ctx,
157. AVCodecContext \*enc\_ctx, const char \*filter\_spec)
158. \{
159. char args\[512\];
160. int ret = 0;
161. AVFilter\*buffersrc = NULL;
162. AVFilter\*buffersink = NULL;
163. AVFilterContext\*buffersrc\_ctx = NULL;
164. AVFilterContext\*buffersink\_ctx = NULL;
165. AVFilterInOut\*outputs = avfilter\_inout\_alloc();
166. AVFilterInOut\*inputs = avfilter\_inout\_alloc();
167. AVFilterGraph\*filter\_graph = avfilter\_graph\_alloc();
168. if (!outputs || !inputs || !filter\_graph) \{
169. ret =AVERROR(ENOMEM);
170. goto end;
171. \}
172. if (dec\_ctx->codec\_type == AVMEDIA\_TYPE\_VIDEO) \{
173. buffersrc =avfilter\_get\_by\_name("buffer");
174. buffersink= avfilter\_get\_by\_name("buffersink");
175. if (!buffersrc || !buffersink) \{
176. av\_log(NULL, AV\_LOG\_ERROR, "filteringsource or sink element not found\\n");
177. ret = AVERROR\_UNKNOWN;
178. goto end;
179. \}
180. \_snprintf(args, sizeof(args),
181. "video\_size=%dx%d:pix\_fmt=%d:time\_base=%d/%d:pixel\_aspect=%d/%d",
182. dec\_ctx->width, dec\_ctx->height, dec\_ctx->pix\_fmt,
183. dec\_ctx->time\_base.num,dec\_ctx->time\_base.den,
184. dec\_ctx->sample\_aspect\_ratio.num,
185. dec\_ctx->sample\_aspect\_ratio.den);
186. ret =avfilter\_graph\_create\_filter(&buffersrc\_ctx, buffersrc, "in",
187. args, NULL, filter\_graph);
188. if (ret < 0) \{
189. av\_log(NULL, AV\_LOG\_ERROR, "Cannotcreate buffer source\\n");
190. goto end;
191. \}
192. ret =avfilter\_graph\_create\_filter(&buffersink\_ctx, buffersink, "out",
193. NULL, NULL, filter\_graph);
194. if (ret < 0) \{
195. av\_log(NULL, AV\_LOG\_ERROR, "Cannotcreate buffer sink\\n");
196. goto end;
197. \}
198. ret =av\_opt\_set\_bin(buffersink\_ctx, "pix\_fmts",
199. (uint8\_t\*)&enc\_ctx->pix\_fmt, sizeof(enc\_ctx->pix\_fmt),
200. AV\_OPT\_SEARCH\_CHILDREN);
201. if (ret < 0) \{
202. av\_log(NULL, AV\_LOG\_ERROR, "Cannot setoutput pixel format\\n");
203. goto end;
204. \}
205. \} else if(dec\_ctx->codec\_type == AVMEDIA\_TYPE\_AUDIO) \{
206. buffersrc = avfilter\_get\_by\_name("abuffer");
207. buffersink= avfilter\_get\_by\_name("abuffersink");
208. if (!buffersrc || !buffersink) \{
209. av\_log(NULL, AV\_LOG\_ERROR, "filteringsource or sink element not found\\n");
210. ret =AVERROR\_UNKNOWN;
211. goto end;
212. \}
213. if (!dec\_ctx->channel\_layout)
214. dec\_ctx->channel\_layout =
215. av\_get\_default\_channel\_layout(dec\_ctx->channels);
216. \_snprintf(args, sizeof(args),
217. "time\_base=%d/%d:sample\_rate=%d:sample\_fmt=%s:channel\_layout=0x%I64x",
218. dec\_ctx->time\_base.num, dec\_ctx->time\_base.den,dec\_ctx->sample\_rate,
219. av\_get\_sample\_fmt\_name(dec\_ctx->sample\_fmt),
220. dec\_ctx->channel\_layout);
221. ret =avfilter\_graph\_create\_filter(&buffersrc\_ctx, buffersrc, "in",
222. args, NULL, filter\_graph);
223. if (ret < 0) \{
224. av\_log(NULL, AV\_LOG\_ERROR, "Cannotcreate audio buffer source\\n");
225. goto end;
226. \}
227. ret =avfilter\_graph\_create\_filter(&buffersink\_ctx, buffersink, "out",
228. NULL, NULL, filter\_graph);
229. if (ret < 0) \{
230. av\_log(NULL, AV\_LOG\_ERROR, "Cannotcreate audio buffer sink\\n");
231. goto end;
232. \}
233. ret = av\_opt\_set\_bin(buffersink\_ctx, "sample\_fmts",
234. (uint8\_t\*)&enc\_ctx->sample\_fmt, sizeof(enc\_ctx->sample\_fmt),
235. AV\_OPT\_SEARCH\_CHILDREN);
236. if (ret < 0) \{
237. av\_log(NULL, AV\_LOG\_ERROR, "Cannot setoutput sample format\\n");
238. goto end;
239. \}
240. ret =av\_opt\_set\_bin(buffersink\_ctx, "channel\_layouts",
241. (uint8\_t\*)&enc\_ctx->channel\_layout,
242. sizeof(enc\_ctx->channel\_layout),AV\_OPT\_SEARCH\_CHILDREN);
243. if (ret < 0) \{
244. av\_log(NULL, AV\_LOG\_ERROR, "Cannot setoutput channel layout\\n");
245. goto end;
246. \}
247. ret =av\_opt\_set\_bin(buffersink\_ctx, "sample\_rates",
248. (uint8\_t\*)&enc\_ctx->sample\_rate, sizeof(enc\_ctx->sample\_rate),
249. AV\_OPT\_SEARCH\_CHILDREN);
250. if (ret < 0) \{
251. av\_log(NULL, AV\_LOG\_ERROR, "Cannot setoutput sample rate\\n");
252. goto end;
253. \}
254. \} else \{
255. ret =AVERROR\_UNKNOWN;
256. goto end;
257. \}
258. /\* Endpoints for the filter graph. \*/
259. outputs->name =av\_strdup("in");
260. outputs->filter\_ctx = buffersrc\_ctx;
261. outputs->pad\_idx = 0;
262. outputs->next = NULL;
263. inputs->name = av\_strdup("out");
264. inputs->filter\_ctx = buffersink\_ctx;
265. inputs->pad\_idx = 0;
266. inputs->next = NULL;
267. if (!outputs->name || !inputs->name) \{
268. ret =AVERROR(ENOMEM);
269. goto end;
270. \}
271. if ((ret = avfilter\_graph\_parse\_ptr(filter\_graph,filter\_spec,
272. &inputs, &outputs, NULL)) < 0)
273. goto end;
274. if ((ret = avfilter\_graph\_config(filter\_graph, NULL))< 0)
275. goto end;
276. /\* Fill FilteringContext \*/
277. fctx->buffersrc\_ctx = buffersrc\_ctx;
278. fctx->buffersink\_ctx = buffersink\_ctx;
279. fctx->filter\_graph= filter\_graph;
280. end:
281. avfilter\_inout\_free(&inputs);
282. avfilter\_inout\_free(&outputs);
283. return ret;
284. \}
285. static int init\_filters(void)
286. \{
287. const char\*filter\_spec;
288. unsigned int i;
289. int ret;
290. filter\_ctx =(FilteringContext \*)av\_malloc\_array(ifmt\_ctx->nb\_streams, sizeof(\*filter\_ctx));
291. if (!filter\_ctx)
292. return AVERROR(ENOMEM);
293. for (i = 0; i < ifmt\_ctx->nb\_streams; i++) \{
294. filter\_ctx\[i\].buffersrc\_ctx =NULL;
295. filter\_ctx\[i\].buffersink\_ctx= NULL;
296. filter\_ctx\[i\].filter\_graph =NULL;
297. if(!(ifmt\_ctx->streams\[i\]->codec->codec\_type == AVMEDIA\_TYPE\_AUDIO
298. ||ifmt\_ctx->streams\[i\]->codec->codec\_type == AVMEDIA\_TYPE\_VIDEO))
299. continue;
300. if (ifmt\_ctx->streams\[i\]->codec->codec\_type== AVMEDIA\_TYPE\_VIDEO)
301. filter\_spec = "null"; /\* passthrough (dummy) filter for video \*/
302. else
303. filter\_spec = "anull"; /\* passthrough (dummy) filter for audio \*/
304. ret =init\_filter(&filter\_ctx\[i\], ifmt\_ctx->streams\[i\]->codec,
305. ofmt\_ctx->streams\[i\]->codec, filter\_spec);
306. if (ret)
307. return ret;
308. \}
309. return 0;
310. \}
311. static intencode\_write\_frame(AVFrame \*filt\_frame, unsignedint stream\_index, int\*got\_frame) \{
312. int ret;
313. int got\_frame\_local;
314. AVPacketenc\_pkt;
315. int (\*enc\_func)(AVCodecContext \*, AVPacket \*, const AVFrame \*, int\*) =
316. (ifmt\_ctx->streams\[stream\_index\]->codec->codec\_type ==
317. AVMEDIA\_TYPE\_VIDEO) ? avcodec\_encode\_video2 : avcodec\_encode\_audio2;
318. if (!got\_frame)
319. got\_frame =&got\_frame\_local;
320. av\_log(NULL,AV\_LOG\_INFO, "Encoding frame\\n");
321. /\* encode filtered frame \*/
322. enc\_pkt.data =NULL;
323. enc\_pkt.size =0;
324. av\_init\_packet(&enc\_pkt);
325. ret =enc\_func(ofmt\_ctx->streams\[stream\_index\]->codec, &enc\_pkt,
326. filt\_frame, got\_frame);
327. av\_frame\_free(&filt\_frame);
328. if (ret < 0)
329. return ret;
330. if (!(\*got\_frame))
331. return 0;
332. /\* prepare packet for muxing \*/
333. enc\_pkt.stream\_index = stream\_index;
334. enc\_pkt.dts =av\_rescale\_q\_rnd(enc\_pkt.dts,
335. ofmt\_ctx->streams\[stream\_index\]->codec->time\_base,
336. ofmt\_ctx->streams\[stream\_index\]->time\_base,
337. (AVRounding)(AV\_ROUND\_NEAR\_INF|AV\_ROUND\_PASS\_MINMAX));
338. enc\_pkt.pts =av\_rescale\_q\_rnd(enc\_pkt.pts,
339. ofmt\_ctx->streams\[stream\_index\]->codec->time\_base,
340. ofmt\_ctx->streams\[stream\_index\]->time\_base,
341. (AVRounding)(AV\_ROUND\_NEAR\_INF|AV\_ROUND\_PASS\_MINMAX));
342. enc\_pkt.duration = av\_rescale\_q(enc\_pkt.duration,
343. ofmt\_ctx->streams\[stream\_index\]->codec->time\_base,
344. ofmt\_ctx->streams\[stream\_index\]->time\_base);
345. av\_log(NULL,AV\_LOG\_DEBUG, "Muxing frame\\n");
346. /\* mux encoded frame \*/
347. ret =av\_interleaved\_write\_frame(ofmt\_ctx, &enc\_pkt);
348. return ret;
349. \}
350. static intfilter\_encode\_write\_frame(AVFrame \*frame, unsignedint stream\_index)
351. \{
352. int ret;
353. AVFrame\*filt\_frame;
354. av\_log(NULL,AV\_LOG\_INFO, "Pushing decoded frame tofilters\\n");
355. /\* push the decoded frame into the filtergraph \*/
356. ret =av\_buffersrc\_add\_frame\_flags(filter\_ctx\[stream\_index\].buffersrc\_ctx,
357. frame,0);
358. if (ret < 0) \{
359. av\_log(NULL, AV\_LOG\_ERROR, "Error whilefeeding the filtergraph\\n");
360. return ret;
361. \}
362. /\* pull filtered frames from the filtergraph \*/
363. while (1) \{
364. filt\_frame= av\_frame\_alloc();
365. if (!filt\_frame) \{
366. ret =AVERROR(ENOMEM);
367. break;
368. \}
369. av\_log(NULL, AV\_LOG\_INFO, "Pullingfiltered frame from filters\\n");
370. ret =av\_buffersink\_get\_frame(filter\_ctx\[stream\_index\].buffersink\_ctx,
371. filt\_frame);
372. if (ret < 0) \{
373. /\* if nomore frames for output - returns AVERROR(EAGAIN)
374.  \* if flushed and no more frames for output - returns AVERROR\_EOF
375.  \* rewrite retcode to 0 to show it as normal procedure completion
376.  \*/
377. if (ret == AVERROR(EAGAIN) || ret == AVERROR\_EOF)
378. ret= 0;
379. av\_frame\_free(&filt\_frame);
380. break;
381. \}
382. filt\_frame->pict\_type = AV\_PICTURE\_TYPE\_NONE;
383. ret =encode\_write\_frame(filt\_frame, stream\_index, NULL);
384. if (ret < 0)
385. break;
386. \}
387. return ret;
388. \}
389. static int flush\_encoder(unsigned intstream\_index)
390. \{
391. int ret;
392. int got\_frame;
393. if(!(ofmt\_ctx->streams\[stream\_index\]->codec->codec->capabilities&
394. CODEC\_CAP\_DELAY))
395. return 0;
396. while (1) \{
397. av\_log(NULL, AV\_LOG\_INFO, "Flushingstream \#%u encoder\\n", stream\_index);
398. ret =encode\_write\_frame(NULL, stream\_index, &got\_frame);
399. if (ret < 0)
400. break;
401. if (!got\_frame)
402. return 0;
403. \}
404. return ret;
405. \}
406. 
407. int\_tmain(int argc, \_TCHAR\* argv\[\])
408. \{
409. int ret;
410. AVPacketpacket;
411. AVFrame \*frame= NULL;
412. enum AVMediaType type;
413. unsigned intstream\_index;
414. unsigned int i;
415. int got\_frame;
416. int (\*dec\_func)(AVCodecContext \*, AVFrame \*, int \*, const AVPacket\*);
417. if (argc != 3) \{
418. av\_log(NULL, AV\_LOG\_ERROR, "Usage: %s<input file> <output file>\\n", argv\[0\]);
419. return 1;
420. \}
421. av\_register\_all();
422. avfilter\_register\_all();
423. if ((ret = open\_input\_file(argv\[1\])) < 0)
424. goto end;
425. if ((ret = open\_output\_file(argv\[2\])) < 0)
426. goto end;
427. if ((ret = init\_filters()) < 0)
428. goto end;
429. /\* read all packets \*/
430. while (1) \{
431. if ((ret= av\_read\_frame(ifmt\_ctx, &packet)) < 0)
432. break;
433. stream\_index = packet.stream\_index;
434. type =ifmt\_ctx->streams\[packet.stream\_index\]->codec->codec\_type;
435. av\_log(NULL, AV\_LOG\_DEBUG, "Demuxergave frame of stream\_index %u\\n",
436. stream\_index);
437. if (filter\_ctx\[stream\_index\].filter\_graph) \{
438. av\_log(NULL, AV\_LOG\_DEBUG, "Going toreencode&filter the frame\\n");
439. frame =av\_frame\_alloc();
440. if (!frame) \{
441. ret = AVERROR(ENOMEM);
442. break;
443. \}
444. packet.dts = av\_rescale\_q\_rnd(packet.dts,
445. ifmt\_ctx->streams\[stream\_index\]->time\_base,
446. ifmt\_ctx->streams\[stream\_index\]->codec->time\_base,
447. (AVRounding)(AV\_ROUND\_NEAR\_INF|AV\_ROUND\_PASS\_MINMAX));
448. packet.pts = av\_rescale\_q\_rnd(packet.pts,
449. ifmt\_ctx->streams\[stream\_index\]->time\_base,
450. ifmt\_ctx->streams\[stream\_index\]->codec->time\_base,
451. (AVRounding)(AV\_ROUND\_NEAR\_INF|AV\_ROUND\_PASS\_MINMAX));
452. dec\_func = (type == AVMEDIA\_TYPE\_VIDEO) ? avcodec\_decode\_video2 :
453. avcodec\_decode\_audio4;
454. ret =dec\_func(ifmt\_ctx->streams\[stream\_index\]->codec, frame,
455. &got\_frame, &packet);
456. if (ret < 0) \{
457. av\_frame\_free(&frame);
458. av\_log(NULL, AV\_LOG\_ERROR, "Decodingfailed\\n");
459. break;
460. \}
461. if (got\_frame) \{
462. frame->pts = av\_frame\_get\_best\_effort\_timestamp(frame);
463. ret= filter\_encode\_write\_frame(frame, stream\_index);
464. av\_frame\_free(&frame);
465. if (ret< 0)
466. goto end;
467. \} else \{
468. av\_frame\_free(&frame);
469. \}
470. \} else \{
471. /\* remux this frame without reencoding \*/
472. packet.dts = av\_rescale\_q\_rnd(packet.dts,
473. ifmt\_ctx->streams\[stream\_index\]->time\_base,
474. ofmt\_ctx->streams\[stream\_index\]->time\_base,
475. (AVRounding)(AV\_ROUND\_NEAR\_INF|AV\_ROUND\_PASS\_MINMAX));
476. packet.pts = av\_rescale\_q\_rnd(packet.pts,
477. ifmt\_ctx->streams\[stream\_index\]->time\_base,
478. ofmt\_ctx->streams\[stream\_index\]->time\_base,
479. (AVRounding)(AV\_ROUND\_NEAR\_INF|AV\_ROUND\_PASS\_MINMAX));
480. ret =av\_interleaved\_write\_frame(ofmt\_ctx, &packet);
481. if (ret < 0)
482. goto end;
483. \}
484. av\_free\_packet(&packet);
485. \}
486. /\* flush filters and encoders \*/
487. for (i = 0; i < ifmt\_ctx->nb\_streams; i++) \{
488. /\* flush filter \*/
489. if (!filter\_ctx\[i\].filter\_graph)
490. continue;
491. ret =filter\_encode\_write\_frame(NULL, i);
492. if (ret < 0) \{
493. av\_log(NULL, AV\_LOG\_ERROR, "Flushingfilter failed\\n");
494. goto end;
495. \}
496. /\* flush encoder \*/
497. ret = flush\_encoder(i);
498. if (ret < 0) \{
499. av\_log(NULL, AV\_LOG\_ERROR, "Flushingencoder failed\\n");
500. goto end;
501. \}
502. \}
503. av\_write\_trailer(ofmt\_ctx);
504. end:
505. av\_free\_packet(&packet);
506. av\_frame\_free(&frame);
507. for (i = 0; i < ifmt\_ctx->nb\_streams; i++) \{
508. avcodec\_close(ifmt\_ctx->streams\[i\]->codec);
509. if (ofmt\_ctx && ofmt\_ctx->nb\_streams >i && ofmt\_ctx->streams\[i\] &&ofmt\_ctx->streams\[i\]->codec)
510. avcodec\_close(ofmt\_ctx->streams\[i\]->codec);
511. if(filter\_ctx && filter\_ctx\[i\].filter\_graph)
512. avfilter\_graph\_free(&filter\_ctx\[i\].filter\_graph);
513. \}
514. av\_free(filter\_ctx);
515. avformat\_close\_input(&ifmt\_ctx);
516. if (ofmt\_ctx &&!(ofmt\_ctx->oformat->flags & AVFMT\_NOFILE))
517. avio\_close(ofmt\_ctx->pb);
518. avformat\_free\_context(ofmt\_ctx);
519. if (ret < 0)
520. av\_log(NULL, AV\_LOG\_ERROR, "Erroroccurred\\n");
521. return (ret? 1:0);
522. \}

程序运行截图：

![SouthEast 3][]

默认情况下运行程序，会将“cuc\_ieschool.ts”转换为“cuc\_ieschool.avi”。调试的时候，可以修改“配置属性->调试->命令参数”中的参数，即可改变转码的输入输出文件。

![SouthEast 4][]

工程下载地址（VC2010）：[http://download.csdn.net/detail/leixiaohua1020/7394649][http_download.csdn.net_detail_leixiaohua1020_7394649]

[SouthEast]: /images/20220731/808f0ffb6acd40b2a80c522af9d1bcef.png
[SouthEast 1]: /images/20220731/b0b496092752437d95f6120e214d0321.png
[100_FFMPEG_SDL_SDL1.x]: http://blog.csdn.net/leixiaohua1020/article/details/8652605
[FFMPEG_YUV_H.264]: http://blog.csdn.net/leixiaohua1020/article/details/25430425
[FFmpeg_AVfilter]: http://blog.csdn.net/leixiaohua1020/article/details/29368911
[SouthEast 2]: /images/20220731/d902955c2cf141379cbbd55e4b36155d.png
[view plain]: http://blog.csdn.net/leixiaohua1020/article/details/26838535#
[CODE]: https://code.csdn.net/assets/CODE_ico.png
[CODE_CODE]: https://code.csdn.net/snippets/361972
[ico_fork.svg]: https://code.csdn.net/assets/ico_fork.svg
[ico_fork.svg 1]: https://code.csdn.net/snippets/361972/fork
[SouthEast 3]: /images/20220731/d0d4040c1ab4487caa05123f58f3633d.png
[SouthEast 4]: /images/20220731/e1f4e72a9dc74a8cbb16b6a0de27081a.png
[http_download.csdn.net_detail_leixiaohua1020_7394649]: http://download.csdn.net/detail/leixiaohua1020/7394649