FFMPEG讀取攝像頭並編碼封裝保存
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參考鏈接1、https://blog.csdn.net/leixiaohua1020/article/details/39702113
參考鏈接2、https://blog.csdn.net/li_wen01/article/details/67631687
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音視頻同步錄製相關文章
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1、 ffmpeg-攝像頭採集保存
2、 ffmpeg音視頻同步-攝像頭採集編碼封裝
3、 ffmpeg-音頻正弦產生並編碼封裝
4、 ffmpeg-音頻實時採集保存
5、 ffmpeg-音頻實時採集編碼封裝
6、 ffmpeg音視頻同步-音視頻實時採集編碼封裝
7、 ffmpeg音視頻同步-音視頻實時採集編碼推流
8、 ffmpeg音視頻同步-音視頻實時採集編碼推流-優化版本
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系統環境：
系統版本：lubuntu 16.04
Ffmpge版本：ffmpeg version N-93527-g1125277
攝像頭：1.3M HD WebCan
虛擬機：Oracle VM VirtualBox 5.2.22
ffmpeg 攝像頭採集指令相關：
指令查看設備 ffmpeg -devices
指令錄製ffmpeg -f video4linux2 -s 640*480 -i /dev/video0 -f flv test.flv
上面的-f flv 指定了封裝器名稱，支持的封裝器可以在/libavformat/muxer_list.c查看。指定了封裝器，不管文件後綴是什麼，都會採用指定的封裝器來封裝文件。
指令指定編碼器H264，幀率25，錄製攝像頭
ffmpeg -f video4linux2 -r 25 -s 640*480 -i /dev/video0 -f flv -vcodec libx264 test.flv
上面的 –vcodec 指定了編碼器。編碼器列表在/libavcodec/codec_list.c,在該結構體下可以看到對應的編碼器名稱。
另外，編碼器desc,在/libavcodec/codec_desc.c下，一般ffprob test.flv,看到的視頻流編碼器信息，就是從這裏獲取。編碼器描述與編碼器通過id連接起來（ps:AV_CODEC_ID_H264）。值得注意的地方是：封裝器要和編碼器搭配上
| 名稱 | 推出機構 | 流媒體 | 支持的視頻編碼 | 支持的音頻編碼 | 目前使用領域 |
|---|---|---|---|---|---|
| AVI | Microsoft Inc. | 不支持 | 幾乎所有格式 | 幾乎所有格式 | BT下載影視 |
| MP4 | MPEG | 支持 | MPEG-2, MPEG-4, H.264, H.263等 | AAC, MPEG-1 Layers I, II, III, AC-3等 | 互聯網視頻網站 |
| TS | MPEG | 支持 | MPEG-1, MPEG-2, MPEG-4, H.264 | MPEG-1 Layers I, II, III, AAC, | IPTV，數字電視 |
| FLV | Adobe Inc. | 支持 | Sorenson, VP6, H.264 | MP3, ADPCM, Linear PCM, AAC等 | 互聯網視頻網站 |
| MKV | CoreCodec Inc. | 支持 | 幾乎所有格式 | 幾乎所有格式 | 互聯網視頻網站 |
| RMVB | Real Networks Inc. | 支持 | RealVideo 8, 9, 10 | AAC, Cook Codec, RealAudio Lossless | BT下載影視 |
上表來源於：https://blog.csdn.net/leixiaohua1020/article/details/18893769 截圖
本章文檔基於 《ffmpeg-攝像頭採集保存》採集攝像頭一幀數據並將其轉化爲YUV420,保存下來，再結合源碼/doc/example/muxing.c例子，僅僅對視頻流進行封裝。
1.簡介
FFmpeg中有一個和多媒體設備交互的類庫：Libavdevice。使用這個庫可以讀取電腦（或者其他設備上）的多媒體設備的數據，或者輸出數據到指定的多媒體設備上
2.源碼
最簡單的基於Libavdevice的攝像頭數據讀取一幀幀YUV數據，經過H.264編碼，封裝成並保存成test.mp4文件：
1. #include <stdlib.h>
2. #include <stdio.h>
3. #include <string.h>
4. #include <math.h>
5.
6. #include <libavutil/avassert.h>
7. #include <libavutil/channel_layout.h>
8. #include <libavutil/opt.h>
9. #include <libavutil/mathematics.h>
10. #include <libavutil/timestamp.h>
11. #include <libavformat/avformat.h>
12. #include <libswscale/swscale.h>
13. #include <libswresample/swresample.h>
14.
15. #define STREAM_DURATION 10.0
16. #define STREAM_FRAME_RATE 25 /* 25 images/s */
17. #define STREAM_PIX_FMT AV_PIX_FMT_YUV420P /* default pix_fmt */
18.
19. #define SCALE_FLAGS SWS_BICUBIC
20.
21. // a wrapper around a single output AVStream
22. typedef struct OutputStream {
23. AVStream *st;
24. AVCodecContext *enc;
25.
26. /* pts of the next frame that will be generated */
27. int64_t next_pts;
28. int samples_count;
29.
30. AVFrame *frame;
31. AVFrame *tmp_frame;
32.
33. float t, tincr, tincr2;
34.
35. struct SwsContext *sws_ctx;
36. struct SwrContext *swr_ctx;
37. } OutputStream;
38.
39.
40. typedef struct IntputDev {
41.
42. AVCodecContext *pCodecCtx;
43. AVCodec *pCodec;
44. AVFormatContext *v_ifmtCtx;
45. int videoindex;
46. struct SwsContext *img_convert_ctx;
47. AVPacket *in_packet;
48. AVFrame *pFrame,*pFrameYUV;
49. }IntputDev;
50.
51. static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt)
52. {
53. AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
54.
55. printf("pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
56. av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base),
57. av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base),
58. av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base),
59. pkt->stream_index);
60. }
61.
62. static int write_frame(AVFormatContext *fmt_ctx, const AVRational *time_base, AVStream *st, AVPacket *pkt)
63. {
64. /* rescale output packet timestamp values from codec to stream timebase */
65. av_packet_rescale_ts(pkt, *time_base, st->time_base);
66. pkt->stream_index = st->index;
67.
68. /* Write the compressed frame to the media file. */
69. log_packet(fmt_ctx, pkt);
70. return av_interleaved_write_frame(fmt_ctx, pkt);
71. }
72.
73. /* Add an output stream. */
74. static void add_stream(OutputStream *ost, AVFormatContext *oc,
75. AVCodec **codec,
76. enum AVCodecID codec_id)
77. {
78. AVCodecContext *c;
79. int i;
80.
81. /* find the encoder */
82. *codec = avcodec_find_encoder(codec_id);
83. if (!(*codec)) {
84. fprintf(stderr, "Could not find encoder for '%s'\n",
85. avcodec_get_name(codec_id));
86. exit(1);
87. }
88.
89. ost->st = avformat_new_stream(oc, NULL);
90. if (!ost->st) {
91. fprintf(stderr, "Could not allocate stream\n");
92. exit(1);
93. }
94. ost->st->id = oc->nb_streams-1;
95. c = avcodec_alloc_context3(*codec);
96. if (!c) {
97. fprintf(stderr, "Could not alloc an encoding context\n");
98. exit(1);
99. }
100. ost->enc = c;
101.
102. switch ((*codec)->type) {
103. case AVMEDIA_TYPE_AUDIO:
104. c->sample_fmt = (*codec)->sample_fmts ?
105. (*codec)->sample_fmts[0] : AV_SAMPLE_FMT_FLTP;
106. c->bit_rate = 64000;
107. c->sample_rate = 44100;
108. if ((*codec)->supported_samplerates) {
109. c->sample_rate = (*codec)->supported_samplerates[0];
110. for (i = 0; (*codec)->supported_samplerates[i]; i++) {
111. if ((*codec)->supported_samplerates[i] == 44100)
112. c->sample_rate = 44100;
113. }
114. }
115. c->channels = av_get_channel_layout_nb_channels(c->channel_layout);
116. c->channel_layout = AV_CH_LAYOUT_STEREO;
117. if ((*codec)->channel_layouts) {
118. c->channel_layout = (*codec)->channel_layouts[0];
119. for (i = 0; (*codec)->channel_layouts[i]; i++) {
120. if ((*codec)->channel_layouts[i] == AV_CH_LAYOUT_STEREO)
121. c->channel_layout = AV_CH_LAYOUT_STEREO;
122. }
123. }
124. c->channels = av_get_channel_layout_nb_channels(c->channel_layout);
125. ost->st->time_base = (AVRational){ 1, c->sample_rate };
126. break;
127.
128. case AVMEDIA_TYPE_VIDEO:
129. c->codec_id = codec_id;
130.
131. c->bit_rate = 400000;
132. /* Resolution must be a multiple of two. */
133. c->width = 640;
134. c->height = 480;
135. /* timebase: This is the fundamental unit of time (in seconds) in terms
136. * of which frame timestamps are represented. For fixed-fps content,
137. * timebase should be 1/framerate and timestamp increments should be
138. * identical to 1. */
139. ost->st->time_base = (AVRational){ 1, STREAM_FRAME_RATE };
140. c->time_base = ost->st->time_base;
141.
142. c->gop_size = 12; /* emit one intra frame every twelve frames at most */
143. c->pix_fmt = STREAM_PIX_FMT;
144. if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
145. /* just for testing, we also add B-frames */
146. c->max_b_frames = 2;
147. }
148. if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
149. /* Needed to avoid using macroblocks in which some coeffs overflow.
150. * This does not happen with normal video, it just happens here as
151. * the motion of the chroma plane does not match the luma plane. */
152. c->mb_decision = 2;
153. }
154. break;
155.
156. default:
157. break;
158. }
159.
160. /* Some formats want stream headers to be separate. */
161. if (oc->oformat->flags & AVFMT_GLOBALHEADER)
162. c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
163. }
164.
165. /**************************************************************/
166.
167.
168. /**************************************************************/
169. /* video output */
170.
171. static AVFrame *alloc_picture(enum AVPixelFormat pix_fmt, int width, int height)
172. {
173. AVFrame *picture;
174. int ret;
175.
176. picture = av_frame_alloc();
177. if (!picture)
178. return NULL;
179.
180. picture->format = pix_fmt;
181. picture->width = width;
182. picture->height = height;
183.
184. /* allocate the buffers for the frame data */
185. ret = av_frame_get_buffer(picture, 32);
186. if (ret < 0) {
187. fprintf(stderr, "Could not allocate frame data.\n");
188. exit(1);
189. }
190.
191. return picture;
192. }
193.
194. static void open_video(AVFormatContext *oc, AVCodec *codec, OutputStream *ost, AVDictionary *opt_arg)
195. {
196. int ret;
197. AVCodecContext *c = ost->enc;
198. AVDictionary *opt = NULL;
199.
200. av_dict_copy(&opt, opt_arg, 0);
201.
202. /* open the codec */
203. ret = avcodec_open2(c, codec, &opt);
204. av_dict_free(&opt);
205. if (ret < 0) {
206. fprintf(stderr, "Could not open video codec: %s\n", av_err2str(ret));
207. exit(1);
208. }
209.
210. /* allocate and init a re-usable frame */
211. ost->frame = alloc_picture(c->pix_fmt, c->width, c->height);
212. if (!ost->frame) {
213. fprintf(stderr, "Could not allocate video frame\n");
214. exit(1);
215. }
216.
217.
218. printf("ost->frame alloc success fmt=%d w=%d h=%d\n",c->pix_fmt,c->width, c->height);
219.
220.
221. /* If the output format is not YUV420P, then a temporary YUV420P
222. * picture is needed too. It is then converted to the required
223. * output format. */
224. ost->tmp_frame = NULL;
225. if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
226. ost->tmp_frame = alloc_picture(AV_PIX_FMT_YUV420P, c->width, c->height);
227. if (!ost->tmp_frame) {
228. fprintf(stderr, "Could not allocate temporary picture\n");
229. exit(1);
230. }
231. }
232.
233. /* copy the stream parameters to the muxer */
234. ret = avcodec_parameters_from_context(ost->st->codecpar, c);
235. if (ret < 0) {
236. fprintf(stderr, "Could not copy the stream parameters\n");
237. exit(1);
238. }
239. }
240.
241.
242.
243.
244. /*
245. * encode one video frame and send it to the muxer
246. * return 1 when encoding is finished, 0 otherwise
247. */
248. static int write_video_frame1(AVFormatContext *oc, OutputStream *ost,AVFrame *frame)
249. {
250. int ret;
251. AVCodecContext *c;
252. int got_packet = 0;
253. AVPacket pkt = { 0 };
254.
255. if(frame==NULL)
256. return 1;
257.
258.
259. c = ost->enc;
260.
261.
262. av_init_packet(&pkt);
263.
264.
265. /* encode the image */
266. ret = avcodec_encode_video2(c, &pkt, frame, &got_packet);
267. if (ret < 0) {
268. fprintf(stderr, "Error encoding video frame: %s\n", av_err2str(ret));
269. exit(1);
270. }
271.
272.
273. printf("--------------video- pkt.pts=%s\n",av_ts2str(pkt.pts));
274.
275. printf("----st.num=%d st.den=%d codec.num=%d codec.den=%d---------\n",ost->st->time_base.num,ost->st->time_base.den,
276. c->time_base.num,c->time_base.den);
277.
278.
279. if (got_packet) {
280. ret = write_frame(oc, &c->time_base, ost->st, &pkt);
281. } else {
282. ret = 0;
283. }
284.
285. if (ret < 0) {
286. fprintf(stderr, "Error while writing video frame: %s\n", av_err2str(ret));
287. exit(1);
288. }
289.
290. return (frame || got_packet) ? 0 : 1;
291. }
292.
293.
294. static AVFrame *get_video_frame1(OutputStream *ost,IntputDev* input,int *got_pic)
295. {
296.
297. int ret, got_picture;
298. AVCodecContext *c = ost->enc;
299. AVFrame * ret_frame=NULL;
300. if (av_compare_ts(ost->next_pts, c->time_base,
301. STREAM_DURATION, (AVRational){ 1, 1 }) >= 0)
302. return NULL;
303.
304. /* when we pass a frame to the encoder, it may keep a reference to it
305. * internally; make sure we do not overwrite it here */
306. if (av_frame_make_writable(ost->frame) < 0)
307. exit(1);
308.
309.
310. if(av_read_frame(input->v_ifmtCtx, input->in_packet)>=0){
311. if(input->in_packet->stream_index==input->videoindex){
312. ret = avcodec_decode_video2(input->pCodecCtx, input->pFrame, &got_picture, input->in_packet);
313. *got_pic=got_picture;
314.
315. if(ret < 0){
316. printf("Decode Error.\n");
317. av_free_packet(input->in_packet);
318. return NULL;
319. }
320. if(got_picture){
321. //sws_scale(input->img_convert_ctx, (const unsigned char* const*)input->pFrame->data, input->pFrame->linesize, 0, input->pCodecCtx->height, ost->frame->data, ost->frame->linesize);
322. sws_scale(input->img_convert_ctx, (const unsigned char* const*)input->pFrame->data, input->pFrame->linesize, 0, input->pCodecCtx->height, ost->frame->data, ost->frame->linesize);
323. ost->frame->pts =ost->next_pts++;
324. ret_frame= ost->frame;
325.
326. }
327. }
328. av_free_packet(input->in_packet);
329. }
330. return ret_frame;
331. }
332. static void close_stream(AVFormatContext *oc, OutputStream *ost)
333. {
334. avcodec_free_context(&ost->enc);
335. av_frame_free(&ost->frame);
336. av_frame_free(&ost->tmp_frame);
337. sws_freeContext(ost->sws_ctx);
338. swr_free(&ost->swr_ctx);
339. }
340.
341. /**************************************************************/
342. /* media file output */
343.
344. int main(int argc, char **argv)
345. {
346. OutputStream video_st = { 0 }, audio_st = { 0 };
347. const char *filename;
348. AVOutputFormat *fmt;
349. AVFormatContext *oc;
350. AVCodec *audio_codec, *video_codec;
351. int ret;
352. int have_video = 0, have_audio = 0;
353. int encode_video = 0, encode_audio = 0;
354. AVDictionary *opt = NULL;
355. int i;
356.
357. if (argc < 2) {
358. printf("usage: %s output_file\n"
359. "API example program to output a media file with libavformat.\n"
360. "This program generates a synthetic audio and video stream, encodes and\n"
361. "muxes them into a file named output_file.\n"
362. "The output format is automatically guessed according to the file extension.\n"
363. "Raw images can also be output by using '%%d' in the filename.\n"
364. "\n", argv[0]);
365. return 1;
366. }
367.
368. filename = argv[1];
369. for (i = 2; i+1 < argc; i+=2) {
370. if (!strcmp(argv[i], "-flags") || !strcmp(argv[i], "-fflags"))
371. av_dict_set(&opt, argv[i]+1, argv[i+1], 0);
372. }
373.
374. /* allocate the output media context */
375. avformat_alloc_output_context2(&oc, NULL, NULL, filename);
376. if (!oc) {
377. printf("Could not deduce output format from file extension: using MPEG.\n");
378. avformat_alloc_output_context2(&oc, NULL, "mpeg", filename);
379. }
380. if (!oc)
381. return 1;
382.
383.
384.
385. //********add camera read***********//
386. IntputDev video_input = { 0 };
387. AVCodecContext *pCodecCtx;
388. AVCodec *pCodec;
389. AVFormatContext *v_ifmtCtx;
390.
391. //Register Device
392. avdevice_register_all();
393.
394. v_ifmtCtx = avformat_alloc_context();
395.
396.
397. //Linux
398. AVInputFormat *ifmt=av_find_input_format("video4linux2");
399. if(avformat_open_input(&v_ifmtCtx,"/dev/video0",ifmt,NULL)!=0){
400. printf("Couldn't open input stream./dev/video0\n");
401. return -1;
402. }
403.
404.
405. if(avformat_find_stream_info(v_ifmtCtx,NULL)<0)
406. {
407. printf("Couldn't find stream information.\n");
408. return -1;
409. }
410.
411. int videoindex=-1;
412. for(i=0; i<v_ifmtCtx->nb_streams; i++)
413. if(v_ifmtCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
414. {
415. videoindex=i;
416. break;
417. }
418. if(videoindex==-1)
419. {
420. printf("Couldn't find a video stream.\n");
421. return -1;
422. }
423.
424. pCodecCtx=v_ifmtCtx->streams[videoindex]->codec;
425. pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
426. if(pCodec==NULL)
427. {
428. printf("Codec not found.\n");
429. return -1;
430. }
431. if(avcodec_open2(pCodecCtx, pCodec,NULL)<0)
432. {
433. printf("Could not open codec.\n");
434. return -1;
435. }
436.
437. AVFrame *pFrame,*pFrameYUV;
438. pFrame=av_frame_alloc();
439. pFrameYUV=av_frame_alloc();
440. unsigned char *out_buffer=(unsigned char *)av_malloc(avpicture_get_size(AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height));
441. avpicture_fill((AVPicture *)pFrameYUV, out_buffer, AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
442.
443. printf("camera width=%d height=%d \n",pCodecCtx->width, pCodecCtx->height);
444.
445.
446. struct SwsContext *img_convert_ctx;
447. img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
448. AVPacket *in_packet=(AVPacket *)av_malloc(sizeof(AVPacket));
449.
450.
451. video_input.img_convert_ctx=img_convert_ctx;
452. video_input.in_packet=in_packet;
453.
454. video_input.pCodecCtx=pCodecCtx;
455. video_input.pCodec=pCodec;
456. video_input.v_ifmtCtx=v_ifmtCtx;
457. video_input.videoindex=videoindex;
458. video_input.pFrame=pFrame;
459. video_input.pFrameYUV=pFrameYUV;
460.
461. //******************************//
462.
463. fmt = oc->oformat;
464.
465. /* Add the audio and video streams using the default format codecs
466. * and initialize the codecs. */
467.
468. printf( "fmt->video_codec = %d\n", fmt->video_codec);
469.
470. if (fmt->video_codec != AV_CODEC_ID_NONE) {
471. add_stream(&video_st, oc, &video_codec, fmt->video_codec);
472. have_video = 1;
473. encode_video = 1;
474. }
475.
476. /* Now that all the parameters are set, we can open the audio and
477. * video codecs and allocate the necessary encode buffers. */
478. if (have_video)
479. open_video(oc, video_codec, &video_st, opt);
480.
481.
482. av_dump_format(oc, 0, filename, 1);
483.
484. /* open the output file, if needed */
485. if (!(fmt->flags & AVFMT_NOFILE)) {
486. ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);
487. if (ret < 0) {
488. fprintf(stderr, "Could not open '%s': %s\n", filename,
489. av_err2str(ret));
490. return 1;
491. }
492. }
493.
494. /* Write the stream header, if any. */
495. ret = avformat_write_header(oc, &opt);
496. if (ret < 0) {
497. fprintf(stderr, "Error occurred when opening output file: %s\n",
498. av_err2str(ret));
499. return 1;
500. }
501.
502. int got_pic;
503.
504. while (encode_video ) {
505. /* select the stream to encode */
506. //encode_video = !write_video_frame(oc, &video_st);
507. AVFrame *frame=get_video_frame1(&video_st,&video_input,&got_pic);
508. if(!got_pic)
509. {
510. usleep(10000);
511. continue;
512.
513. }
514. encode_video = !write_video_frame1(oc, &video_st,frame);
515. }
516.
517.
518. /* Write the trailer, if any. The trailer must be written before you
519. * close the CodecContexts open when you wrote the header; otherwise
520. * av_write_trailer() may try to use memory that was freed on
521. * av_codec_close(). */
522. av_write_trailer(oc);
523.
524. sws_freeContext(video_input.img_convert_ctx);
525.
526.
527. avcodec_close(video_input.pCodecCtx);
528. av_free(video_input.pFrameYUV);
529. av_free(video_input.pFrame);
530. avformat_close_input(&video_input.v_ifmtCtx);
531.
532.
533. /* Close each codec. */
534. if (have_video)
535. close_stream(oc, &video_st);
536.
537. if (!(fmt->flags & AVFMT_NOFILE))
538. /* Close the output file. */
539. avio_closep(&oc->pb);
540.
541. /* free the stream */
542. avformat_free_context(oc);
543.
544. return 0;
545. }
3.驗證
3.1 編譯
1. #!/bin/sh
2. export PKG_CONFIG_PATH=/home/quange/ffmpeg_build/lib/pkgconfig/:$PKG_CONFIG_PATH
3. gcc ffmpeg_get_camera_muxing.c -g -o ffmpeg_get_camera_muxing.out -lSDLmain -lSDL `pkg-config "libavcodec" --cflags --libs` `pkg-config "libavformat" --cflags --libs` `pkg-config "libavutil" --cflags --libs` `pkg-config "libswscale" --cflags --libs` `pkg-config "libavdevice" --cflags --libs`
3.2 結果測試
使用軟件vlc打開test.mp4
