This patch introduces PCM dumping support between AVFilter links, intended for
audio debugging.
It adds a configure-time option `--dumpdir=PATH` to specify the output
directory for raw PCM data (default: /tmp/).
Two commands are exposed to control dumping:
- dump_raw_start <dst_filter_name>
- dump_raw_stop <dst_filter_name>
Dump files are written as: srcname-dstname-channel.pcm
Supports packed and planar formats. File descriptors are managed automatically
and work only on audio links.
Example usage:
avfilter_process_command(filter, "dump_raw_start", "volume", NULL, 0, 0);
This feature helps developers debug filter behavior by inspecting intermediate
audio data.
---
>From 6a31c85afd2800c09076c1e2b7c734c7b719f73d Mon Sep 17 00:00:00 2001
From: Yibo Fang <blueybf...@outlook.com>
Date: Wed, 23 Apr 2025 09:17:51 +0800
Subject: [PATCH 1/1] avfilter: add PCM dumping between filters for audio
debugging
This patch adds the ability to dump raw PCM audio data between AVFilter links.
It introduces a configure-time option `--dumpdir=PATH` to control the output
directory of dump files (default: /tmp/). This feature is helpful for debugging
filter behavior and verifying audio processing.
Two filter commands are added:
- dump_raw_start <dst_filter_name>
- dump_raw_stop <dst_filter_name>
The PCM files are written in the format: srcname-dstname-<channel>.pcm.
Supports both packed and planar formats. File descriptors are automatically
managed. Works only on audio links.
Example usage:
avfilter_process_command(filter, "dump_raw_start", "volume", NULL, 0, 0);
Signed-off-by: Yibo Fang <blueybf...@outlook.com>
---
configure | 7 +++
libavfilter/avfilter.c | 110 +++++++++++++++++++++++++++++++++++++++++
libavfilter/avfilter.h | 4 ++
3 files changed, 121 insertions(+)
diff --git a/configure b/configure
index c94b8eac43..381633749d 100755
--- a/configure
+++ b/configure
@@ -524,6 +524,7 @@ Developer options (useful when working on FFmpeg itself):
--disable-large-tests disable tests that use a large amount of memory
--disable-ptx-compression don't compress CUDA PTX code even when possible
--disable-version-tracking don't include the git/release version in the build
+ --dumpdir=PATH location of pcm dump files to save.
NOTE: Object files are built at the place where configure is launched.
EOF
@@ -2690,6 +2691,7 @@ PATHS_LIST="
prefix
shlibdir
install_name_dir
+ dumpdir
"
CMDLINE_SET="
@@ -4123,6 +4125,9 @@ incdir_default='${prefix}/include'
libdir_default='${prefix}/lib'
mandir_default='${prefix}/share/man'
+# runtime path
+dumpdir_default='/tmp/'
+
# toolchain
ar_default="ar"
cc_default="gcc"
@@ -8118,6 +8123,7 @@ DOCDIR=\$(DESTDIR)$docdir
MANDIR=\$(DESTDIR)$mandir
PKGCONFIGDIR=\$(DESTDIR)$pkgconfigdir
INSTALL_NAME_DIR=$install_name_dir
+DUMPDIR=$dumpdir
SRC_PATH=$source_path
SRC_LINK=$source_link
ifndef MAIN_MAKEFILE
@@ -8267,6 +8273,7 @@ cat > $TMPH <<EOF
#define CONFIG_THIS_YEAR 2025
#define FFMPEG_DATADIR "$(eval c_escape $datadir)"
#define AVCONV_DATADIR "$(eval c_escape $datadir)"
+#define FFMPEG_DUMPDIR "$(eval c_escape $dumpdir)"
#define CC_IDENT "$(c_escape ${cc_ident:-Unknown compiler})"
#define OS_NAME $target_os
#define EXTERN_PREFIX "${extern_prefix}"
diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index 64c1075c40..9fc6308544 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -19,6 +19,9 @@
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
+#include <fcntl.h>
+#include <unistd.h>
+
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/bprint.h"
@@ -195,6 +198,66 @@ int avfilter_link(AVFilterContext *src, unsigned srcpad,
return 0;
}
+static av_cold void link_uninit_dump_pcm(AVFilterLink *link, int stop)
+{
+ if (link->dump_pcm_fds) {
+ int i;
+ for (i = 0; i < link->nb_dump_pcm_fds; i++) {
+ if (link->dump_pcm_fds[i])
+ close(link->dump_pcm_fds[i]);
+ }
+ av_free(link->dump_pcm_fds);
+ link->dump_pcm_fds = NULL;
+ link->nb_dump_pcm_fds = 0;
+ }
+
+ if (stop)
+ link->dump_pcm = 0;
+}
+
+static av_cold int link_init_dump_pcm(AVFilterLink *link)
+{
+ char path[4096];
+ int fd, i;
+
+ link->nb_dump_pcm_fds = av_sample_fmt_is_planar(link->format)?
link->ch_layout.nb_channels : 1;
+ link->dump_pcm_fds = av_malloc_array(link->nb_dump_pcm_fds, sizeof(int));
+ if (!link->dump_pcm_fds)
+ return AVERROR(ENOMEM);
+
+ for (i = 0; i < link->nb_dump_pcm_fds; i++) {
+ snprintf(path, sizeof(path), FFMPEG_DUMPDIR"%.16s-%.8s-%d.pcm",
link->src->name, link->dst->name, i);
+ fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+ if (fd < 0) {
+ link_uninit_dump_pcm(link, 1);
+ return AVERROR(errno);
+ }
+ link->dump_pcm_fds[i] = fd;
+ }
+
+ return 0;
+}
+
+static int filter_set_dump_pcm(AVFilterContext *filter, const char *target,
int set)
+{
+ int i;
+
+ for (i = 0; i < filter->nb_outputs; i++) {
+ AVFilterLink *link = filter->outputs[i];
+ if (!target || !strcmp(link->dst->name, target)) {
+ if (set) {
+ link->dump_pcm = 1;
+ } else
+ link_uninit_dump_pcm(link, 1);
+
+ if (target)
+ return 0;
+ }
+ }
+
+ return target ? AVERROR(EINVAL) : 0;
+}
+
static void link_free(AVFilterLink **link)
{
FilterLinkInternal *li;
@@ -208,6 +271,8 @@ static void link_free(AVFilterLink **link)
av_channel_layout_uninit(&(*link)->ch_layout);
av_frame_side_data_free(&(*link)->side_data, &(*link)->nb_side_data);
+ link_uninit_dump_pcm(*link, 1);
+
av_buffer_unref(&li->l.hw_frames_ctx);
av_freep(link);
@@ -617,6 +682,10 @@ int avfilter_process_command(AVFilterContext *filter,
const char *cmd, const cha
if (res == local_res)
av_log(filter, AV_LOG_INFO, "%s", res);
return 0;
+ }else if(!strcmp(cmd, "dump_raw_start")) {
+ return filter_set_dump_pcm(filter, arg, 1);
+ }else if(!strcmp(cmd, "dump_raw_stop")) {
+ return filter_set_dump_pcm(filter, arg, 0);
}else if(!strcmp(cmd, "enable")) {
return set_enable_expr(fffilterctx(filter), arg);
}else if (fffilter(filter->filter)->process_command) {
@@ -1050,6 +1119,41 @@ fail:
return ret;
}
+static int link_dump_frame(AVFilterLink *link, AVFrame *frame)
+{
+ int samples_size, ret;
+
+ if (!link->dump_pcm_fds) {
+ ret = link_init_dump_pcm(link);
+ if (ret < 0)
+ return ret;
+ }
+
+ samples_size = av_get_bytes_per_sample(frame->format) * frame->nb_samples;
+ if (av_sample_fmt_is_planar(frame->format)) {
+ int i;
+ for (i = 0; i < link->nb_dump_pcm_fds && i <
frame->ch_layout.nb_channels; i++) {
+ if (i < AV_NUM_DATA_POINTERS) {
+ ret = write(link->dump_pcm_fds[i], frame->data[i],
samples_size);
+ } else
+ ret = write(link->dump_pcm_fds[i], frame->extended_data[i -
AV_NUM_DATA_POINTERS], samples_size);
+
+ if (ret < 0)
+ goto err;
+ }
+ } else {
+ ret = write(link->dump_pcm_fds[0], frame->data[0], samples_size *
frame->ch_layout.nb_channels);
+ if (ret < 0)
+ goto err;
+
+ }
+
+ return 0;
+err:
+ link_uninit_dump_pcm(link, 1);
+ return AVERROR(errno);
+}
+
int ff_filter_frame(AVFilterLink *link, AVFrame *frame)
{
FilterLinkInternal * const li = ff_link_internal(link);
@@ -1087,6 +1191,12 @@ int ff_filter_frame(AVFilterLink *link, AVFrame *frame)
link->time_base);
}
+ if (link->dump_pcm && link->type == AVMEDIA_TYPE_AUDIO) {
+ ret = link_dump_frame(link, frame);
+ if (ret < 0)
+ av_log(link->dst, AV_LOG_ERROR, "Dump pcm files failed with %d\n",
ret);
+ }
+
li->frame_blocked_in = li->frame_wanted_out = 0;
li->l.frame_count_in++;
li->l.sample_count_in += frame->nb_samples;
diff --git a/libavfilter/avfilter.h b/libavfilter/avfilter.h
index a89d3cf658..6d04b9da77 100644
--- a/libavfilter/avfilter.h
+++ b/libavfilter/avfilter.h
@@ -404,6 +404,10 @@ struct AVFilterLink {
int sample_rate; ///< samples per second
AVChannelLayout ch_layout; ///< channel layout of current buffer (see
libavutil/channel_layout.h)
+ int dump_pcm; ///< flag to dump pcm
+ int *dump_pcm_fds; ///< dump files
+ unsigned nb_dump_pcm_fds; ///< number of dump file
+
/**
* Define the time base used by the PTS of the frames/samples
* which will pass through this link.
--
2.34.1
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