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/mem.h"
34 #include "libavutil/opt.h"
36 #include "audio.h"
37 #include "avfilter.h"
38 #include "filters.h"
39 #include "formats.h"
40 
41 #define MAX_CHANNELS 64
42 
43 typedef struct PanContext {
44  const AVClass *class;
45  char *args;
51 
53  /* channel mapping specific */
55  struct SwrContext *swr;
56 } PanContext;
57 
58 static void skip_spaces(char **arg)
59 {
60  int len = 0;
61 
62  sscanf(*arg, " %n", &len);
63  *arg += len;
64 }
65 
66 static int parse_channel_name(char **arg, int *rchannel, int *rnamed)
67 {
68  char buf[8];
69  int len, channel_id = 0;
70 
72  /* try to parse a channel name, e.g. "FL" */
73  if (sscanf(*arg, "%7[A-Z]%n", buf, &len)) {
74  channel_id = av_channel_from_string(buf);
75  if (channel_id < 0)
76  return channel_id;
77 
78  *rchannel = channel_id;
79  *rnamed = 1;
80  *arg += len;
81  return 0;
82  }
83  /* try to parse a channel number, e.g. "c2" */
84  if (sscanf(*arg, "c%d%n", &channel_id, &len) &&
85  channel_id >= 0 && channel_id < MAX_CHANNELS) {
86  *rchannel = channel_id;
87  *rnamed = 0;
88  *arg += len;
89  return 0;
90  }
91  return AVERROR(EINVAL);
92 }
93 
94 static int are_gains_pure(const PanContext *pan)
95 {
96  int i, j;
97 
98  for (i = 0; i < MAX_CHANNELS; i++) {
99  int nb_gain = 0;
100 
101  for (j = 0; j < MAX_CHANNELS; j++) {
102  double gain = pan->gain[i][j];
103 
104  /* channel mapping is effective only if 0% or 100% of a channel is
105  * selected... */
106  if (gain != 0. && gain != 1.)
107  return 0;
108  /* ...and if the output channel is only composed of one input */
109  if (gain && nb_gain++)
110  return 0;
111  }
112  }
113  return 1;
114 }
115 
117 {
118  PanContext *const pan = ctx->priv;
119  char *arg, *arg0, *tokenizer, *args = av_strdup(pan->args);
120  int out_ch_id, in_ch_id, len, named, ret, sign = 1;
121  int nb_in_channels[2] = { 0, 0 }; // number of unnamed and named input channels
122  int used_out_ch[MAX_CHANNELS] = {0};
123  double gain;
124 
125  if (!pan->args) {
127  "pan filter needs a channel layout and a set "
128  "of channel definitions as parameter\n");
129  return AVERROR(EINVAL);
130  }
131  if (!args)
132  return AVERROR(ENOMEM);
133  arg = av_strtok(args, "|", &tokenizer);
134  if (!arg) {
135  av_log(ctx, AV_LOG_ERROR, "Channel layout not specified\n");
136  ret = AVERROR(EINVAL);
137  goto fail;
138  }
140  &pan->nb_output_channels, arg, ctx);
141  if (ret < 0)
142  goto fail;
143 
144  if (pan->nb_output_channels > MAX_CHANNELS) {
146  "af_pan supports a maximum of %d channels. "
147  "Feel free to ask for a higher limit.\n", MAX_CHANNELS);
149  goto fail;
150  }
151 
152  /* parse channel specifications */
153  while ((arg = arg0 = av_strtok(NULL, "|", &tokenizer))) {
154  int used_in_ch[MAX_CHANNELS] = {0};
155  /* channel name */
156  if (parse_channel_name(&arg, &out_ch_id, &named)) {
158  "Expected out channel name, got \"%.8s\"\n", arg);
159  ret = AVERROR(EINVAL);
160  goto fail;
161  }
162  if (named) {
163  if ((out_ch_id = av_channel_layout_index_from_channel(&pan->out_channel_layout, out_ch_id)) < 0) {
165  "Channel \"%.8s\" does not exist in the chosen layout\n", arg0);
166  ret = AVERROR(EINVAL);
167  goto fail;
168  }
169  }
170  if (out_ch_id < 0 || out_ch_id >= pan->nb_output_channels) {
172  "Invalid out channel name \"%.8s\"\n", arg0);
173  ret = AVERROR(EINVAL);
174  goto fail;
175  }
176  if (used_out_ch[out_ch_id]) {
178  "Can not reference out channel %d twice\n", out_ch_id);
179  ret = AVERROR(EINVAL);
180  goto fail;
181  }
182  used_out_ch[out_ch_id] = 1;
183  skip_spaces(&arg);
184  if (*arg == '=') {
185  arg++;
186  } else if (*arg == '<') {
187  pan->need_renorm |= (int64_t)1 << out_ch_id;
188  arg++;
189  } else {
191  "Syntax error after channel name in \"%.8s\"\n", arg0);
192  ret = AVERROR(EINVAL);
193  goto fail;
194  }
195  /* gains */
196  sign = 1;
197  while (1) {
198  gain = 1;
199  if (sscanf(arg, "%lf%n *%n", &gain, &len, &len))
200  arg += len;
201  if (parse_channel_name(&arg, &in_ch_id, &named)){
203  "Expected in channel name, got \"%.8s\"\n", arg);
204  ret = AVERROR(EINVAL);
205  goto fail;
206  }
207  nb_in_channels[named]++;
208  if (nb_in_channels[!named]) {
210  "Can not mix named and numbered channels\n");
211  ret = AVERROR(EINVAL);
212  goto fail;
213  }
214  if (used_in_ch[in_ch_id]) {
216  "Can not reference in channel %d twice\n", in_ch_id);
217  ret = AVERROR(EINVAL);
218  goto fail;
219  }
220  used_in_ch[in_ch_id] = 1;
221  pan->gain[out_ch_id][in_ch_id] = sign * gain;
222  skip_spaces(&arg);
223  if (!*arg)
224  break;
225  if (*arg == '-') {
226  sign = -1;
227  } else if (*arg != '+') {
228  av_log(ctx, AV_LOG_ERROR, "Syntax error near \"%.8s\"\n", arg);
229  ret = AVERROR(EINVAL);
230  goto fail;
231  } else {
232  sign = 1;
233  }
234  arg++;
235  }
236  }
237  pan->need_renumber = !!nb_in_channels[1];
238  pan->pure_gains = are_gains_pure(pan);
239 
240  ret = 0;
241 fail:
242  av_free(args);
243  return ret;
244 }
245 
247  AVFilterFormatsConfig **cfg_in,
248  AVFilterFormatsConfig **cfg_out)
249 {
250  const PanContext *pan = ctx->priv;
252  int ret;
253 
254  // inlink supports any channel layout
256  if ((ret = ff_channel_layouts_ref(layouts, &cfg_in[0]->channel_layouts)) < 0)
257  return ret;
258 
259  // outlink supports only requested output channel layout
260  layouts = NULL;
262  return ret;
263  return ff_channel_layouts_ref(layouts, &cfg_out[0]->channel_layouts);
264 }
265 
267 {
268  AVFilterContext *ctx = link->dst;
269  PanContext *pan = ctx->priv;
270  char buf[1024], *cur;
271  int i, j, k, r, ret;
272  double t;
273 
274  if (pan->need_renumber) {
275  // input channels were given by their name: renumber them
276  for (i = j = 0; i < MAX_CHANNELS; i++) {
278  for (k = 0; k < pan->nb_output_channels; k++)
279  pan->gain[k][j] = pan->gain[k][i];
280  j++;
281  }
282  }
283  }
284 
285  // sanity check; can't be done in query_formats since the inlink
286  // channel layout is unknown at that time
290  "af_pan supports a maximum of %d channels. "
291  "Feel free to ask for a higher limit.\n", MAX_CHANNELS);
292  return AVERROR_PATCHWELCOME;
293  }
294 
295  // init libswresample context
296  ret = swr_alloc_set_opts2(&pan->swr,
299  0, ctx);
300  if (ret < 0)
301  return AVERROR(ENOMEM);
302 
303  // gains are pure, init the channel mapping
304  if (pan->pure_gains) {
305 
306  // get channel map from the pure gains
307  for (i = 0; i < pan->nb_output_channels; i++) {
308  int ch_id = -1;
309  for (j = 0; j < link->ch_layout.nb_channels; j++) {
310  if (pan->gain[i][j]) {
311  ch_id = j;
312  break;
313  }
314  }
315  pan->channel_map[i] = ch_id;
316  }
317 
318  av_opt_set_chlayout(pan->swr, "uchl", &pan->out_channel_layout, 0);
320  } else {
321  // renormalize
322  for (i = 0; i < pan->nb_output_channels; i++) {
323  if (!((pan->need_renorm >> i) & 1))
324  continue;
325  t = 0;
326  for (j = 0; j < link->ch_layout.nb_channels; j++)
327  t += fabs(pan->gain[i][j]);
328  if (t > -1E-5 && t < 1E-5) {
329  // t is almost 0 but not exactly, this is probably a mistake
330  if (t)
332  "Degenerate coefficients while renormalizing\n");
333  continue;
334  }
335  for (j = 0; j < link->ch_layout.nb_channels; j++)
336  pan->gain[i][j] /= t;
337  }
338  swr_set_matrix(pan->swr, pan->gain[0], pan->gain[1] - pan->gain[0]);
339  }
340 
341  r = swr_init(pan->swr);
342  if (r < 0)
343  return r;
344 
345  // summary
346  for (i = 0; i < pan->nb_output_channels; i++) {
347  cur = buf;
348  for (j = 0; j < link->ch_layout.nb_channels; j++) {
349  r = snprintf(cur, buf + sizeof(buf) - cur, "%s%.3g i%d",
350  j ? " + " : "", pan->gain[i][j], j);
351  cur += FFMIN(buf + sizeof(buf) - cur, r);
352  }
353  av_log(ctx, AV_LOG_VERBOSE, "o%d = %s\n", i, buf);
354  }
355  // add channel mapping summary if possible
356  if (pan->pure_gains) {
357  av_log(ctx, AV_LOG_INFO, "Pure channel mapping detected:");
358  for (i = 0; i < pan->nb_output_channels; i++)
359  if (pan->channel_map[i] < 0)
360  av_log(ctx, AV_LOG_INFO, " M");
361  else
362  av_log(ctx, AV_LOG_INFO, " %d", pan->channel_map[i]);
363  av_log(ctx, AV_LOG_INFO, "\n");
364  return 0;
365  }
366  return 0;
367 }
368 
369 static int filter_frame(AVFilterLink *inlink, AVFrame *insamples)
370 {
371  int ret;
372  int n = insamples->nb_samples;
373  AVFilterLink *const outlink = inlink->dst->outputs[0];
374  AVFrame *outsamples = ff_get_audio_buffer(outlink, n);
375  PanContext *pan = inlink->dst->priv;
376 
377  if (!outsamples) {
378  av_frame_free(&insamples);
379  return AVERROR(ENOMEM);
380  }
381  swr_convert(pan->swr, outsamples->extended_data, n,
382  (void *)insamples->extended_data, n);
383  av_frame_copy_props(outsamples, insamples);
384  if ((ret = av_channel_layout_copy(&outsamples->ch_layout, &outlink->ch_layout)) < 0) {
385  av_frame_free(&outsamples);
386  av_frame_free(&insamples);
387  return ret;
388  }
389 
390  av_frame_free(&insamples);
391  return ff_filter_frame(outlink, outsamples);
392 }
393 
395 {
396  PanContext *pan = ctx->priv;
397  swr_free(&pan->swr);
399 }
400 
401 #define OFFSET(x) offsetof(PanContext, x)
402 
403 static const AVOption pan_options[] = {
405  { NULL }
406 };
407 
409 
410 static const AVFilterPad pan_inputs[] = {
411  {
412  .name = "default",
413  .type = AVMEDIA_TYPE_AUDIO,
414  .config_props = config_props,
415  .filter_frame = filter_frame,
416  },
417 };
418 
420  .name = "pan",
421  .description = NULL_IF_CONFIG_SMALL("Remix channels with coefficients (panning)."),
422  .priv_size = sizeof(PanContext),
423  .priv_class = &pan_class,
424  .init = init,
425  .uninit = uninit,
429 };
ff_get_audio_buffer
AVFrame * ff_get_audio_buffer(AVFilterLink *link, int nb_samples)
Request an audio samples buffer with a specific set of permissions.
Definition: audio.c:98
AVFilterChannelLayouts
A list of supported channel layouts.
Definition: formats.h:85
AV_LOG_WARNING
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:215
PanContext::out_channel_layout
AVChannelLayout out_channel_layout
Definition: af_pan.c:46
r
const char * r
Definition: vf_curves.c:127
AVERROR
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
opt.h
ff_filter_frame
int ff_filter_frame(AVFilterLink *link, AVFrame *frame)
Send a frame of data to the next filter.
Definition: avfilter.c:1025
ff_channel_layouts_ref
int ff_channel_layouts_ref(AVFilterChannelLayouts *f, AVFilterChannelLayouts **ref)
Add *ref as a new reference to f.
Definition: formats.c:673
layouts
enum MovChannelLayoutTag * layouts
Definition: mov_chan.c:335
int64_t
long long int64_t
Definition: coverity.c:34
inlink
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
Definition: filter_design.txt:212
av_frame_free
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:162
ff_all_channel_counts
AVFilterChannelLayouts * ff_all_channel_counts(void)
Construct an AVFilterChannelLayouts coding for any channel layout, with known or unknown disposition.
Definition: formats.c:621
FILTER_INPUTS
#define FILTER_INPUTS(array)
Definition: filters.h:262
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:389
AVOption
AVOption.
Definition: opt.h:429
config_props
static int config_props(AVFilterLink *link)
Definition: af_pan.c:266
AV_LOG_VERBOSE
#define AV_LOG_VERBOSE
Detailed information.
Definition: log.h:225
swr_set_channel_mapping
int swr_set_channel_mapping(struct SwrContext *s, const int *channel_map)
Set a customized input channel mapping.
Definition: swresample.c:33
AVFilter::name
const char * name
Filter name.
Definition: avfilter.h:205
AVChannelLayout::nb_channels
int nb_channels
Number of channels in this layout.
Definition: channel_layout.h:321
swr_set_matrix
int swr_set_matrix(struct SwrContext *s, const double *matrix, int stride)
Set a customized remix matrix.
Definition: rematrix.c:65
ff_af_pan
const AVFilter ff_af_pan
Definition: af_pan.c:419
formats.h
fail
#define fail()
Definition: checkasm.h:188
AVFrame::ch_layout
AVChannelLayout ch_layout
Channel layout of the audio data.
Definition: frame.h:790
AVFilterPad
A filter pad used for either input or output.
Definition: filters.h:38
swr_convert
int attribute_align_arg swr_convert(struct SwrContext *s, uint8_t *const *out_arg, int out_count, const uint8_t *const *in_arg, int in_count)
Convert audio.
Definition: swresample.c:719
AV_OPT_FLAG_AUDIO_PARAM
#define AV_OPT_FLAG_AUDIO_PARAM
Definition: opt.h:357
PanContext::pure_gains
int pure_gains
Definition: af_pan.c:52
PanContext::swr
struct SwrContext * swr
Definition: af_pan.c:55
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:209
av_cold
#define av_cold
Definition: attributes.h:90
swr_init
av_cold int swr_init(struct SwrContext *s)
Initialize context after user parameters have been set.
Definition: swresample.c:140
PanContext::args
char * args
Definition: af_pan.c:45
query_formats
static int query_formats(const AVFilterContext *ctx, AVFilterFormatsConfig **cfg_in, AVFilterFormatsConfig **cfg_out)
Definition: af_pan.c:246
filter_frame
static int filter_frame(AVFilterLink *inlink, AVFrame *insamples)
Definition: af_pan.c:369
AVMEDIA_TYPE_AUDIO
@ AVMEDIA_TYPE_AUDIO
Definition: avutil.h:202
av_strtok
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:178
skip_spaces
static void skip_spaces(char **arg)
Definition: af_pan.c:58
filters.h
ctx
AVFormatContext * ctx
Definition: movenc.c:49
SwrContext
The libswresample context.
Definition: swresample_internal.h:95
FILTER_OUTPUTS
#define FILTER_OUTPUTS(array)
Definition: filters.h:263
E
#define E
Definition: avdct.c:33
link
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
Definition: filter_design.txt:23
ff_parse_channel_layout
int ff_parse_channel_layout(AVChannelLayout *ret, int *nret, const char *arg, void *log_ctx)
Parse a channel layout or a corresponding integer representation.
Definition: audio.c:123
arg
const char * arg
Definition: jacosubdec.c:67
PanContext::need_renorm
int64_t need_renorm
Definition: af_pan.c:48
AVClass
Describe the class of an AVClass context structure.
Definition: log.h:75
fabs
static __device__ float fabs(float a)
Definition: cuda_runtime.h:182
NULL
#define NULL
Definition: coverity.c:32
AVERROR_PATCHWELCOME
#define AVERROR_PATCHWELCOME
Not yet implemented in FFmpeg, patches welcome.
Definition: error.h:64
av_frame_copy_props
int av_frame_copy_props(AVFrame *dst, const AVFrame *src)
Copy only "metadata" fields from src to dst.
Definition: frame.c:713
ff_audio_default_filterpad
const AVFilterPad ff_audio_default_filterpad[1]
An AVFilterPad array whose only entry has name "default" and is of type AVMEDIA_TYPE_AUDIO.
Definition: audio.c:34
pan_inputs
static const AVFilterPad pan_inputs[]
Definition: af_pan.c:410
are_gains_pure
static int are_gains_pure(const PanContext *pan)
Definition: af_pan.c:94
pan_options
static const AVOption pan_options[]
Definition: af_pan.c:403
ff_add_channel_layout
int ff_add_channel_layout(AVFilterChannelLayouts **l, const AVChannelLayout *channel_layout)
Definition: formats.c:521
PanContext::nb_output_channels
int nb_output_channels
Definition: af_pan.c:50
swresample.h
AVFilterFormatsConfig
Lists of formats / etc.
Definition: avfilter.h:111
OFFSET
#define OFFSET(x)
Definition: af_pan.c:401
AV_OPT_FLAG_FILTERING_PARAM
#define AV_OPT_FLAG_FILTERING_PARAM
A generic parameter which can be set by the user for filtering.
Definition: opt.h:381
swr_alloc_set_opts2
int swr_alloc_set_opts2(struct SwrContext **ps, const AVChannelLayout *out_ch_layout, enum AVSampleFormat out_sample_fmt, int out_sample_rate, const AVChannelLayout *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:40
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:94
AVChannelLayout
An AVChannelLayout holds information about the channel layout of audio data.
Definition: channel_layout.h:311
av_opt_set_chlayout
int av_opt_set_chlayout(void *obj, const char *name, const AVChannelLayout *channel_layout, int search_flags)
Definition: opt.c:992
AVFrame::sample_rate
int sample_rate
Sample rate of the audio data.
Definition: frame.h:588
PanContext::need_renumber
int need_renumber
Definition: af_pan.c:49
swr_free
av_cold void swr_free(SwrContext **ss)
Free the given SwrContext and set the pointer to NULL.
Definition: swresample.c:121
AVFrame::format
int format
format of the frame, -1 if unknown or unset Values correspond to enum AVPixelFormat for video frames,...
Definition: frame.h:476
PanContext::channel_map
int channel_map[MAX_CHANNELS]
Definition: af_pan.c:54
AV_LOG_INFO
#define AV_LOG_INFO
Standard information.
Definition: log.h:220
AVFrame::nb_samples
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:469
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:256
AVFrame::extended_data
uint8_t ** extended_data
pointers to the data planes/channels.
Definition: frame.h:450
FILTER_QUERY_FUNC2
#define FILTER_QUERY_FUNC2(func)
Definition: filters.h:239
FFMIN
#define FFMIN(a, b)
Definition: macros.h:49
len
int len
Definition: vorbis_enc_data.h:426
AVFilterPad::name
const char * name
Pad name.
Definition: filters.h:44
AVFilter
Filter definition.
Definition: avfilter.h:201
ret
ret
Definition: filter_design.txt:187
av_channel_from_string
enum AVChannel av_channel_from_string(const char *str)
This is the inverse function of av_channel_name().
Definition: channel_layout.c:150
channel_layout.h
av_channel_layout_index_from_channel
int av_channel_layout_index_from_channel(const AVChannelLayout *channel_layout, enum AVChannel channel)
Get the index of a given channel in a channel layout.
Definition: channel_layout.c:708
avfilter.h
av_channel_layout_uninit
void av_channel_layout_uninit(AVChannelLayout *channel_layout)
Free any allocated data in the channel layout and reset the channel count to 0.
Definition: channel_layout.c:437
init
static av_cold int init(AVFilterContext *ctx)
Definition: af_pan.c:116
AVFilterContext
An instance of a filter.
Definition: avfilter.h:457
av_channel_layout_copy
int av_channel_layout_copy(AVChannelLayout *dst, const AVChannelLayout *src)
Make a copy of a channel layout.
Definition: channel_layout.c:444
av_strdup
char * av_strdup(const char *s)
Duplicate a string.
Definition: mem.c:272
MAX_CHANNELS
#define MAX_CHANNELS
Definition: af_pan.c:41
mem.h
audio.h
av_free
#define av_free(p)
Definition: tableprint_vlc.h:33
PanContext
Definition: af_pan.c:43
parse_channel_name
static int parse_channel_name(char **arg, int *rchannel, int *rnamed)
Definition: af_pan.c:66
channel_layouts
static const uint16_t channel_layouts[7]
Definition: dca_lbr.c:112
PanContext::gain
double gain[MAX_CHANNELS][MAX_CHANNELS]
Definition: af_pan.c:47
AVFILTER_DEFINE_CLASS
AVFILTER_DEFINE_CLASS(pan)
uninit
static av_cold void uninit(AVFilterContext *ctx)
Definition: af_pan.c:394
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:27
avstring.h
AV_OPT_TYPE_STRING
@ AV_OPT_TYPE_STRING
Underlying C type is a uint8_t* that is either NULL or points to a C string allocated with the av_mal...
Definition: opt.h:276
snprintf
#define snprintf
Definition: snprintf.h:34