FFmpeg
af_pan.c
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1 /*
2  * Copyright (c) 2002 Anders Johansson <ajh@atri.curtin.edu.au>
3  * Copyright (c) 2011 Clément Bœsch <u pkh me>
4  * Copyright (c) 2011 Nicolas George <nicolas.george@normalesup.org>
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16  * GNU Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 /**
24  * @file
25  * Audio panning filter (channels mixing)
26  * Original code written by Anders Johansson for MPlayer,
27  * reimplemented for FFmpeg.
28  */
29 
30 #include <stdio.h>
31 #include "libavutil/avstring.h"
33 #include "libavutil/opt.h"
35 #include "audio.h"
36 #include "avfilter.h"
37 #include "formats.h"
38 #include "internal.h"
39 
40 #define MAX_CHANNELS 64
41 
42 typedef struct PanContext {
43  const AVClass *class;
44  char *args;
47  int64_t need_renorm;
50 
52  /* channel mapping specific */
54  struct SwrContext *swr;
55 } PanContext;
56 
57 static void skip_spaces(char **arg)
58 {
59  int len = 0;
60 
61  sscanf(*arg, " %n", &len);
62  *arg += len;
63 }
64 
65 static int parse_channel_name(char **arg, int *rchannel, int *rnamed)
66 {
67  char buf[8];
68  int len, i, channel_id = 0;
69  int64_t layout, layout0;
70 
71  skip_spaces(arg);
72  /* try to parse a channel name, e.g. "FL" */
73  if (sscanf(*arg, "%7[A-Z]%n", buf, &len)) {
74  layout0 = layout = av_get_channel_layout(buf);
75  /* channel_id <- first set bit in layout */
76  for (i = 32; i > 0; i >>= 1) {
77  if (layout >= (int64_t)1 << i) {
78  channel_id += i;
79  layout >>= i;
80  }
81  }
82  /* reject layouts that are not a single channel */
83  if (channel_id >= MAX_CHANNELS || layout0 != (int64_t)1 << channel_id)
84  return AVERROR(EINVAL);
85  *rchannel = channel_id;
86  *rnamed = 1;
87  *arg += len;
88  return 0;
89  }
90  /* try to parse a channel number, e.g. "c2" */
91  if (sscanf(*arg, "c%d%n", &channel_id, &len) &&
92  channel_id >= 0 && channel_id < MAX_CHANNELS) {
93  *rchannel = channel_id;
94  *rnamed = 0;
95  *arg += len;
96  return 0;
97  }
98  return AVERROR(EINVAL);
99 }
100 
102 {
103  PanContext *const pan = ctx->priv;
104  char *arg, *arg0, *tokenizer, *args = av_strdup(pan->args);
105  int out_ch_id, in_ch_id, len, named, ret, sign = 1;
106  int nb_in_channels[2] = { 0, 0 }; // number of unnamed and named input channels
107  int used_out_ch[MAX_CHANNELS] = {0};
108  double gain;
109 
110  if (!pan->args) {
111  av_log(ctx, AV_LOG_ERROR,
112  "pan filter needs a channel layout and a set "
113  "of channel definitions as parameter\n");
114  return AVERROR(EINVAL);
115  }
116  if (!args)
117  return AVERROR(ENOMEM);
118  arg = av_strtok(args, "|", &tokenizer);
119  if (!arg) {
120  av_log(ctx, AV_LOG_ERROR, "Channel layout not specified\n");
121  ret = AVERROR(EINVAL);
122  goto fail;
123  }
125  &pan->nb_output_channels, arg, ctx);
126  if (ret < 0)
127  goto fail;
128 
129  /* parse channel specifications */
130  while ((arg = arg0 = av_strtok(NULL, "|", &tokenizer))) {
131  int used_in_ch[MAX_CHANNELS] = {0};
132  /* channel name */
133  if (parse_channel_name(&arg, &out_ch_id, &named)) {
134  av_log(ctx, AV_LOG_ERROR,
135  "Expected out channel name, got \"%.8s\"\n", arg);
136  ret = AVERROR(EINVAL);
137  goto fail;
138  }
139  if (named) {
140  if (!((pan->out_channel_layout >> out_ch_id) & 1)) {
141  av_log(ctx, AV_LOG_ERROR,
142  "Channel \"%.8s\" does not exist in the chosen layout\n", arg0);
143  ret = AVERROR(EINVAL);
144  goto fail;
145  }
146  /* get the channel number in the output channel layout:
147  * out_channel_layout & ((1 << out_ch_id) - 1) are all the
148  * channels that come before out_ch_id,
149  * so their count is the index of out_ch_id */
150  out_ch_id = av_get_channel_layout_nb_channels(pan->out_channel_layout & (((int64_t)1 << out_ch_id) - 1));
151  }
152  if (out_ch_id < 0 || out_ch_id >= pan->nb_output_channels) {
153  av_log(ctx, AV_LOG_ERROR,
154  "Invalid out channel name \"%.8s\"\n", arg0);
155  ret = AVERROR(EINVAL);
156  goto fail;
157  }
158  if (used_out_ch[out_ch_id]) {
159  av_log(ctx, AV_LOG_ERROR,
160  "Can not reference out channel %d twice\n", out_ch_id);
161  ret = AVERROR(EINVAL);
162  goto fail;
163  }
164  used_out_ch[out_ch_id] = 1;
165  skip_spaces(&arg);
166  if (*arg == '=') {
167  arg++;
168  } else if (*arg == '<') {
169  pan->need_renorm |= (int64_t)1 << out_ch_id;
170  arg++;
171  } else {
172  av_log(ctx, AV_LOG_ERROR,
173  "Syntax error after channel name in \"%.8s\"\n", arg0);
174  ret = AVERROR(EINVAL);
175  goto fail;
176  }
177  /* gains */
178  sign = 1;
179  while (1) {
180  gain = 1;
181  if (sscanf(arg, "%lf%n *%n", &gain, &len, &len))
182  arg += len;
183  if (parse_channel_name(&arg, &in_ch_id, &named)){
184  av_log(ctx, AV_LOG_ERROR,
185  "Expected in channel name, got \"%.8s\"\n", arg);
186  ret = AVERROR(EINVAL);
187  goto fail;
188  }
189  nb_in_channels[named]++;
190  if (nb_in_channels[!named]) {
191  av_log(ctx, AV_LOG_ERROR,
192  "Can not mix named and numbered channels\n");
193  ret = AVERROR(EINVAL);
194  goto fail;
195  }
196  if (used_in_ch[in_ch_id]) {
197  av_log(ctx, AV_LOG_ERROR,
198  "Can not reference in channel %d twice\n", in_ch_id);
199  ret = AVERROR(EINVAL);
200  goto fail;
201  }
202  used_in_ch[in_ch_id] = 1;
203  pan->gain[out_ch_id][in_ch_id] = sign * gain;
204  skip_spaces(&arg);
205  if (!*arg)
206  break;
207  if (*arg == '-') {
208  sign = -1;
209  } else if (*arg != '+') {
210  av_log(ctx, AV_LOG_ERROR, "Syntax error near \"%.8s\"\n", arg);
211  ret = AVERROR(EINVAL);
212  goto fail;
213  } else {
214  sign = 1;
215  }
216  arg++;
217  }
218  }
219  pan->need_renumber = !!nb_in_channels[1];
220 
221  ret = 0;
222 fail:
223  av_free(args);
224  return ret;
225 }
226 
227 static int are_gains_pure(const PanContext *pan)
228 {
229  int i, j;
230 
231  for (i = 0; i < MAX_CHANNELS; i++) {
232  int nb_gain = 0;
233 
234  for (j = 0; j < MAX_CHANNELS; j++) {
235  double gain = pan->gain[i][j];
236 
237  /* channel mapping is effective only if 0% or 100% of a channel is
238  * selected... */
239  if (gain != 0. && gain != 1.)
240  return 0;
241  /* ...and if the output channel is only composed of one input */
242  if (gain && nb_gain++)
243  return 0;
244  }
245  }
246  return 1;
247 }
248 
250 {
251  PanContext *pan = ctx->priv;
252  AVFilterLink *inlink = ctx->inputs[0];
253  AVFilterLink *outlink = ctx->outputs[0];
256  int ret;
257 
258  pan->pure_gains = are_gains_pure(pan);
259  /* libswr supports any sample and packing formats */
261  return ret;
262 
263  formats = ff_all_samplerates();
264  if ((ret = ff_set_common_samplerates(ctx, formats)) < 0)
265  return ret;
266 
267  // inlink supports any channel layout
268  layouts = ff_all_channel_counts();
269  if ((ret = ff_channel_layouts_ref(layouts, &inlink->out_channel_layouts)) < 0)
270  return ret;
271 
272  // outlink supports only requested output channel layout
273  layouts = NULL;
274  if ((ret = ff_add_channel_layout(&layouts,
277  return ret;
278  return ff_channel_layouts_ref(layouts, &outlink->in_channel_layouts);
279 }
280 
282 {
283  AVFilterContext *ctx = link->dst;
284  PanContext *pan = ctx->priv;
285  char buf[1024], *cur;
286  int i, j, k, r;
287  double t;
288 
289  if (pan->need_renumber) {
290  // input channels were given by their name: renumber them
291  for (i = j = 0; i < MAX_CHANNELS; i++) {
292  if ((link->channel_layout >> i) & 1) {
293  for (k = 0; k < pan->nb_output_channels; k++)
294  pan->gain[k][j] = pan->gain[k][i];
295  j++;
296  }
297  }
298  }
299 
300  // sanity check; can't be done in query_formats since the inlink
301  // channel layout is unknown at that time
302  if (link->channels > MAX_CHANNELS ||
304  av_log(ctx, AV_LOG_ERROR,
305  "af_pan supports a maximum of %d channels. "
306  "Feel free to ask for a higher limit.\n", MAX_CHANNELS);
307  return AVERROR_PATCHWELCOME;
308  }
309 
310  // init libswresample context
311  pan->swr = swr_alloc_set_opts(pan->swr,
312  pan->out_channel_layout, link->format, link->sample_rate,
313  link->channel_layout, link->format, link->sample_rate,
314  0, ctx);
315  if (!pan->swr)
316  return AVERROR(ENOMEM);
317  if (!link->channel_layout) {
318  if (av_opt_set_int(pan->swr, "ich", link->channels, 0) < 0)
319  return AVERROR(EINVAL);
320  }
321  if (!pan->out_channel_layout) {
322  if (av_opt_set_int(pan->swr, "och", pan->nb_output_channels, 0) < 0)
323  return AVERROR(EINVAL);
324  }
325 
326  // gains are pure, init the channel mapping
327  if (pan->pure_gains) {
328 
329  // get channel map from the pure gains
330  for (i = 0; i < pan->nb_output_channels; i++) {
331  int ch_id = -1;
332  for (j = 0; j < link->channels; j++) {
333  if (pan->gain[i][j]) {
334  ch_id = j;
335  break;
336  }
337  }
338  pan->channel_map[i] = ch_id;
339  }
340 
341  av_opt_set_int(pan->swr, "icl", pan->out_channel_layout, 0);
342  av_opt_set_int(pan->swr, "uch", pan->nb_output_channels, 0);
344  } else {
345  // renormalize
346  for (i = 0; i < pan->nb_output_channels; i++) {
347  if (!((pan->need_renorm >> i) & 1))
348  continue;
349  t = 0;
350  for (j = 0; j < link->channels; j++)
351  t += fabs(pan->gain[i][j]);
352  if (t > -1E-5 && t < 1E-5) {
353  // t is almost 0 but not exactly, this is probably a mistake
354  if (t)
355  av_log(ctx, AV_LOG_WARNING,
356  "Degenerate coefficients while renormalizing\n");
357  continue;
358  }
359  for (j = 0; j < link->channels; j++)
360  pan->gain[i][j] /= t;
361  }
362  av_opt_set_int(pan->swr, "icl", link->channel_layout, 0);
363  av_opt_set_int(pan->swr, "ocl", pan->out_channel_layout, 0);
364  swr_set_matrix(pan->swr, pan->gain[0], pan->gain[1] - pan->gain[0]);
365  }
366 
367  r = swr_init(pan->swr);
368  if (r < 0)
369  return r;
370 
371  // summary
372  for (i = 0; i < pan->nb_output_channels; i++) {
373  cur = buf;
374  for (j = 0; j < link->channels; j++) {
375  r = snprintf(cur, buf + sizeof(buf) - cur, "%s%.3g i%d",
376  j ? " + " : "", pan->gain[i][j], j);
377  cur += FFMIN(buf + sizeof(buf) - cur, r);
378  }
379  av_log(ctx, AV_LOG_VERBOSE, "o%d = %s\n", i, buf);
380  }
381  // add channel mapping summary if possible
382  if (pan->pure_gains) {
383  av_log(ctx, AV_LOG_INFO, "Pure channel mapping detected:");
384  for (i = 0; i < pan->nb_output_channels; i++)
385  if (pan->channel_map[i] < 0)
386  av_log(ctx, AV_LOG_INFO, " M");
387  else
388  av_log(ctx, AV_LOG_INFO, " %d", pan->channel_map[i]);
389  av_log(ctx, AV_LOG_INFO, "\n");
390  return 0;
391  }
392  return 0;
393 }
394 
395 static int filter_frame(AVFilterLink *inlink, AVFrame *insamples)
396 {
397  int ret;
398  int n = insamples->nb_samples;
399  AVFilterLink *const outlink = inlink->dst->outputs[0];
400  AVFrame *outsamples = ff_get_audio_buffer(outlink, n);
401  PanContext *pan = inlink->dst->priv;
402 
403  if (!outsamples) {
404  av_frame_free(&insamples);
405  return AVERROR(ENOMEM);
406  }
407  swr_convert(pan->swr, outsamples->extended_data, n,
408  (void *)insamples->extended_data, n);
409  av_frame_copy_props(outsamples, insamples);
410  outsamples->channel_layout = outlink->channel_layout;
411  outsamples->channels = outlink->channels;
412 
413  ret = ff_filter_frame(outlink, outsamples);
414  av_frame_free(&insamples);
415  return ret;
416 }
417 
419 {
420  PanContext *pan = ctx->priv;
421  swr_free(&pan->swr);
422 }
423 
424 #define OFFSET(x) offsetof(PanContext, x)
425 
426 static const AVOption pan_options[] = {
427  { "args", NULL, OFFSET(args), AV_OPT_TYPE_STRING, { .str = NULL }, CHAR_MIN, CHAR_MAX, AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_FILTERING_PARAM },
428  { NULL }
429 };
430 
432 
433 static const AVFilterPad pan_inputs[] = {
434  {
435  .name = "default",
436  .type = AVMEDIA_TYPE_AUDIO,
437  .config_props = config_props,
438  .filter_frame = filter_frame,
439  },
440  { NULL }
441 };
442 
443 static const AVFilterPad pan_outputs[] = {
444  {
445  .name = "default",
446  .type = AVMEDIA_TYPE_AUDIO,
447  },
448  { NULL }
449 };
450 
452  .name = "pan",
453  .description = NULL_IF_CONFIG_SMALL("Remix channels with coefficients (panning)."),
454  .priv_size = sizeof(PanContext),
455  .priv_class = &pan_class,
456  .init = init,
457  .uninit = uninit,
459  .inputs = pan_inputs,
460  .outputs = pan_outputs,
461 };
#define NULL
Definition: coverity.c:32
char * args
Definition: af_pan.c:44
#define MAX_CHANNELS
Definition: af_pan.c:40
double gain[MAX_CHANNELS][MAX_CHANNELS]
Definition: af_pan.c:46
This structure describes decoded (raw) audio or video data.
Definition: frame.h:295
AVOption.
Definition: opt.h:246
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:182
Main libavfilter public API header.
#define AV_OPT_FLAG_AUDIO_PARAM
Definition: opt.h:278
static int config_props(AVFilterLink *link)
Definition: af_pan.c:281
int av_get_channel_layout_nb_channels(uint64_t channel_layout)
Return the number of channels in the channel layout.
static int filter_frame(AVFilterLink *inlink, AVFrame *insamples)
Definition: af_pan.c:395
const char * name
Pad name.
Definition: internal.h:60
uint64_t av_get_channel_layout(const char *name)
Return a channel layout id that matches name, or 0 if no match is found.
AVFilterLink ** inputs
array of pointers to input links
Definition: avfilter.h:346
int ff_channel_layouts_ref(AVFilterChannelLayouts *f, AVFilterChannelLayouts **ref)
Add *ref as a new reference to f.
Definition: formats.c:434
int ff_filter_frame(AVFilterLink *link, AVFrame *frame)
Send a frame of data to the next filter.
Definition: avfilter.c:1093
#define av_cold
Definition: attributes.h:82
AVOptions.
int need_renumber
Definition: af_pan.c:48
#define AV_LOG_VERBOSE
Detailed information.
Definition: log.h:192
#define av_log(a,...)
AVFilterFormats * ff_all_formats(enum AVMediaType type)
Return a list of all formats supported by FFmpeg for the given media type.
Definition: formats.c:349
static const AVFilterPad pan_inputs[]
Definition: af_pan.c:433
static const AVOption pan_options[]
Definition: af_pan.c:426
A filter pad used for either input or output.
Definition: internal.h:54
libswresample public header
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:259
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
int ff_set_common_formats(AVFilterContext *ctx, AVFilterFormats *formats)
A helper for query_formats() which sets all links to the same list of formats.
Definition: formats.c:569
int ff_add_channel_layout(AVFilterChannelLayouts **l, uint64_t channel_layout)
Definition: formats.c:342
AVFrame * ff_get_audio_buffer(AVFilterLink *link, int nb_samples)
Request an audio samples buffer with a specific set of permissions.
Definition: audio.c:86
#define AV_OPT_FLAG_FILTERING_PARAM
a generic parameter which can be set by the user for filtering
Definition: opt.h:292
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:202
The libswresample context.
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:186
const char * r
Definition: vf_curves.c:114
void * priv
private data for use by the filter
Definition: avfilter.h:353
int ff_parse_channel_layout(int64_t *ret, int *nret, const char *arg, void *log_ctx)
Parse a channel layout or a corresponding integer representation.
Definition: formats.c:663
static int query_formats(AVFilterContext *ctx)
Definition: af_pan.c:249
const char * arg
Definition: jacosubdec.c:66
int av_opt_set_int(void *obj, const char *name, int64_t val, int search_flags)
Definition: opt.c:568
struct SwrContext * swr
Definition: af_pan.c:54
#define fail()
Definition: checkasm.h:122
static int are_gains_pure(const PanContext *pan)
Definition: af_pan.c:227
uint64_t channel_layout
Channel layout of the audio data.
Definition: frame.h:472
int channels
number of audio channels, only used for audio.
Definition: frame.h:601
audio channel layout utility functions
#define E
Definition: avdct.c:32
#define FFMIN(a, b)
Definition: common.h:96
int swr_set_matrix(struct SwrContext *s, const double *matrix, int stride)
Set a customized remix matrix.
Definition: rematrix.c:64
int pure_gains
Definition: af_pan.c:51
static void skip_spaces(char **arg)
Definition: af_pan.c:57
AVFormatContext * ctx
Definition: movenc.c:48
struct SwrContext * swr_alloc_set_opts(struct SwrContext *s, int64_t out_ch_layout, enum AVSampleFormat out_sample_fmt, int out_sample_rate, int64_t in_ch_layout, enum AVSampleFormat in_sample_fmt, int in_sample_rate, int log_offset, void *log_ctx)
Allocate SwrContext if needed and set/reset common parameters.
Definition: swresample.c:59
AVFilter ff_af_pan
Definition: af_pan.c:451
int n
Definition: avisynth_c.h:760
static const AVFilterPad outputs[]
Definition: af_acontrast.c:203
A list of supported channel layouts.
Definition: formats.h:85
#define AVERROR_PATCHWELCOME
Not yet implemented in FFmpeg, patches welcome.
Definition: error.h:62
int64_t out_channel_layout
Definition: af_pan.c:45
#define AV_LOG_INFO
Standard information.
Definition: log.h:187
char * av_strdup(const char *s)
Duplicate a string.
Definition: mem.c:251
av_cold void swr_free(SwrContext **ss)
Free the given SwrContext and set the pointer to NULL.
Definition: swresample.c:137
void * buf
Definition: avisynth_c.h:766
int swr_set_channel_mapping(struct SwrContext *s, const int *channel_map)
Set a customized input channel mapping.
Definition: swresample.c:52
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several inputs
Describe the class of an AVClass context structure.
Definition: log.h:67
Filter definition.
Definition: avfilter.h:144
#define OFFSET(x)
Definition: af_pan.c:424
int64_t need_renorm
Definition: af_pan.c:47
int channel_map[MAX_CHANNELS]
Definition: af_pan.c:53
const char * name
Filter name.
Definition: avfilter.h:148
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a link
#define snprintf
Definition: snprintf.h:34
int attribute_align_arg swr_convert(struct SwrContext *s, uint8_t *out_arg[SWR_CH_MAX], int out_count, const uint8_t *in_arg[SWR_CH_MAX], int in_count)
Definition: swresample.c:714
AVFilterLink ** outputs
array of pointers to output links
Definition: avfilter.h:350
enum MovChannelLayoutTag * layouts
Definition: mov_chan.c:434
AVFilterFormats * ff_all_samplerates(void)
Definition: formats.c:394
AVFILTER_DEFINE_CLASS(pan)
The exact code depends on how similar the blocks are and how related they are to the and needs to apply these operations to the correct inlink or outlink if there are several Macros are available to factor that when no extra processing is inlink
char * av_strtok(char *s, const char *delim, char **saveptr)
Split the string into several tokens which can be accessed by successive calls to av_strtok()...
Definition: avstring.c:184
static int parse_channel_name(char **arg, int *rchannel, int *rnamed)
Definition: af_pan.c:65
#define av_free(p)
int len
static av_cold int init(AVFilterContext *ctx)
Definition: af_pan.c:101
A list of supported formats for one end of a filter link.
Definition: formats.h:64
An instance of a filter.
Definition: avfilter.h:338
#define FF_COUNT2LAYOUT(c)
Encode a channel count as a channel layout.
Definition: formats.h:102
formats
Definition: signature.h:48
internal API functions
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later.That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another.Frame references ownership and permissions
AVFilterChannelLayouts * ff_all_channel_counts(void)
Construct an AVFilterChannelLayouts coding for any channel layout, with known or unknown disposition...
Definition: formats.c:409
uint8_t ** extended_data
pointers to the data planes/channels.
Definition: frame.h:342
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:361
static av_cold void uninit(AVFilterContext *ctx)
Definition: af_pan.c:418
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel layout
int ff_set_common_samplerates(AVFilterContext *ctx, AVFilterFormats *samplerates)
Definition: formats.c:557
int av_frame_copy_props(AVFrame *dst, const AVFrame *src)
Copy only "metadata" fields from src to dst.
Definition: frame.c:654
av_cold int swr_init(struct SwrContext *s)
Initialize context after user parameters have been set.
Definition: swresample.c:152
static const AVFilterPad pan_outputs[]
Definition: af_pan.c:443
int nb_output_channels
Definition: af_pan.c:49