[FFmpeg-devel] [PATCH] lavc: add null codecs

[Anton Khirnov <anton@khirnov.net>]

They discard all input without ever returning any output. Useful for
development.
---
 libavcodec/Makefile     |  4 ++
 libavcodec/allcodecs.c  |  6 +++
 libavcodec/codec_desc.c | 12 ++++++
 libavcodec/codec_id.h   | 10 +++++
 libavcodec/null.c       | 96 +++++++++++++++++++++++++++++++++++++++++
 libavcodec/version.h    |  2 +-
 6 files changed, 129 insertions(+), 1 deletion(-)
 create mode 100644 libavcodec/null.c

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 2d9710923d..098ab18353 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -219,6 +219,8 @@ OBJS-$(CONFIG_AMRWB_DECODER)           += amrwbdec.o celp_filters.o   \
                                           acelp_pitch_delay.o
 OBJS-$(CONFIG_AMV_ENCODER)             += mjpegenc.o mjpegenc_common.o
 OBJS-$(CONFIG_ANM_DECODER)             += anm.o
+OBJS-$(CONFIG_ANULL_DECODER)           += null.o
+OBJS-$(CONFIG_ANULL_ENCODER)           += null.o
 OBJS-$(CONFIG_ANSI_DECODER)            += ansi.o cga_data.o
 OBJS-$(CONFIG_APAC_DECODER)            += apac.o
 OBJS-$(CONFIG_APE_DECODER)             += apedec.o
@@ -746,6 +748,8 @@ OBJS-$(CONFIG_VCR1_DECODER)            += vcr1.o
 OBJS-$(CONFIG_VMDAUDIO_DECODER)        += vmdaudio.o
 OBJS-$(CONFIG_VMDVIDEO_DECODER)        += vmdvideo.o
 OBJS-$(CONFIG_VMNC_DECODER)            += vmnc.o
+OBJS-$(CONFIG_VNULL_DECODER)           += null.o
+OBJS-$(CONFIG_VNULL_ENCODER)           += null.o
 OBJS-$(CONFIG_VORBIS_DECODER)          += vorbisdec.o vorbisdsp.o vorbis.o \
                                           vorbis_data.o
 OBJS-$(CONFIG_VORBIS_ENCODER)          += vorbisenc.o vorbis.o \
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index f728c6c82e..7452002f24 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -882,6 +882,12 @@ extern const FFCodec ff_vp9_qsv_decoder;
 extern const FFCodec ff_vp9_vaapi_encoder;
 extern const FFCodec ff_vp9_qsv_encoder;
 
+// null codecs
+extern const FFCodec ff_vnull_decoder;
+extern const FFCodec ff_vnull_encoder;
+extern const FFCodec ff_anull_decoder;
+extern const FFCodec ff_anull_encoder;
+
 // The iterate API is not usable with ossfuzz due to the excessive size of binaries created
 #if CONFIG_OSSFUZZ
 const FFCodec * codec_list[] = {
diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
index 2272232ed6..b3bec2f659 100644
--- a/libavcodec/codec_desc.c
+++ b/libavcodec/codec_desc.c
@@ -1923,6 +1923,12 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .long_name = NULL_IF_CONFIG_SMALL("ViewQuest VQC"),
         .props     = AV_CODEC_PROP_LOSSY,
     },
+    {
+        .id        = AV_CODEC_ID_VNULL,
+        .type      = AVMEDIA_TYPE_VIDEO,
+        .name      = "vnull",
+        .long_name = NULL_IF_CONFIG_SMALL("Null video codec"),
+    },
 
     /* various PCM "codecs" */
     {
@@ -3339,6 +3345,12 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .long_name = NULL_IF_CONFIG_SMALL("FTR Voice"),
         .props     = AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSY,
     },
+    {
+        .id        = AV_CODEC_ID_ANULL,
+        .type      = AVMEDIA_TYPE_AUDIO,
+        .name      = "anull",
+        .long_name = NULL_IF_CONFIG_SMALL("Null audio codec"),
+    },
 
     /* subtitle codecs */
     {
diff --git a/libavcodec/codec_id.h b/libavcodec/codec_id.h
index 5ec3fd4b30..c197e956b7 100644
--- a/libavcodec/codec_id.h
+++ b/libavcodec/codec_id.h
@@ -320,6 +320,11 @@ enum AVCodecID {
     AV_CODEC_ID_WBMP,
     AV_CODEC_ID_MEDIA100,
     AV_CODEC_ID_VQC,
+    /**
+     * Dummy null video codec, useful mainly for development and debugging.
+     * Null encoder/decoder discard all input and never return any output.
+     */
+    AV_CODEC_ID_VNULL,
 
     /* various PCM "codecs" */
     AV_CODEC_ID_FIRST_AUDIO = 0x10000,     ///< A dummy id pointing at the start of audio codecs
@@ -534,6 +539,11 @@ enum AVCodecID {
     AV_CODEC_ID_MISC4,
     AV_CODEC_ID_APAC,
     AV_CODEC_ID_FTR,
+    /**
+     * Dummy null audio codec, useful mainly for development and debugging.
+     * Null encoder/decoder discard all input and never return any output.
+     */
+    AV_CODEC_ID_ANULL,
 
     /* subtitle codecs */
     AV_CODEC_ID_FIRST_SUBTITLE = 0x17000,          ///< A dummy ID pointing at the start of subtitle codecs.
diff --git a/libavcodec/null.c b/libavcodec/null.c
new file mode 100644
index 0000000000..df75a077ae
--- /dev/null
+++ b/libavcodec/null.c
@@ -0,0 +1,96 @@
+/*
+ * Null codecs
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "config_components.h"
+
+#include "codec_internal.h"
+#include "decode.h"
+#include "encode.h"
+
+#if CONFIG_VNULL_DECODER || CONFIG_ANULL_DECODER
+static int null_decode(AVCodecContext *avctx, AVFrame *frame,
+                       int *got_frame, AVPacket *avpkt)
+{
+    *got_frame = 0;
+    return avpkt->size;
+}
+
+#if CONFIG_VNULL_DECODER
+const FFCodec ff_vnull_decoder = {
+    .p.name         = "vnull",
+    CODEC_LONG_NAME("null video"),
+    .p.type         = AVMEDIA_TYPE_VIDEO,
+    .p.id           = AV_CODEC_ID_VNULL,
+    .p.capabilities = AV_CODEC_CAP_DR1,
+    FF_CODEC_DECODE_CB(null_decode),
+};
+#endif
+
+#if CONFIG_ANULL_DECODER
+const FFCodec ff_anull_decoder = {
+    .p.name         = "anull",
+    CODEC_LONG_NAME("null audio"),
+    .p.type         = AVMEDIA_TYPE_AUDIO,
+    .p.id           = AV_CODEC_ID_ANULL,
+    .p.capabilities = AV_CODEC_CAP_DR1,
+    FF_CODEC_DECODE_CB(null_decode),
+};
+#endif
+
+#endif
+
+#if CONFIG_VNULL_ENCODER || CONFIG_ANULL_ENCODER
+static int null_encode(AVCodecContext *avctx, AVPacket *pkt,
+                       const AVFrame *frame, int *got_packet)
+{
+    *got_packet = 0;
+    return 0;
+}
+
+#if CONFIG_VNULL_ENCODER
+const FFCodec ff_vnull_encoder = {
+    .p.name         = "vnull",
+    CODEC_LONG_NAME("null video"),
+    .p.type         = AVMEDIA_TYPE_VIDEO,
+    .p.id           = AV_CODEC_ID_VNULL,
+    FF_CODEC_ENCODE_CB(null_encode),
+};
+#endif
+
+#if CONFIG_ANULL_ENCODER
+const FFCodec ff_anull_encoder = {
+    .p.name         = "anull",
+    CODEC_LONG_NAME("null audio"),
+    .p.type         = AVMEDIA_TYPE_AUDIO,
+    .p.id           = AV_CODEC_ID_ANULL,
+    .p.capabilities = AV_CODEC_CAP_VARIABLE_FRAME_SIZE,
+    .p.sample_fmts  = (const enum AVSampleFormat[]){
+        AV_SAMPLE_FMT_U8,  AV_SAMPLE_FMT_U8P,
+        AV_SAMPLE_FMT_S16, AV_SAMPLE_FMT_S16P,
+        AV_SAMPLE_FMT_S32, AV_SAMPLE_FMT_S32P,
+        AV_SAMPLE_FMT_S64, AV_SAMPLE_FMT_S64P,
+        AV_SAMPLE_FMT_FLT, AV_SAMPLE_FMT_FLTP,
+        AV_SAMPLE_FMT_DBL, AV_SAMPLE_FMT_DBLP,
+    },
+    FF_CODEC_ENCODE_CB(null_encode),
+};
+#endif
+
+#endif
diff --git a/libavcodec/version.h b/libavcodec/version.h
index dfd3d5d7e5..7ac8d2b2fe 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -29,7 +29,7 @@
 
 #include "version_major.h"
 
-#define LIBAVCODEC_VERSION_MINOR  57
+#define LIBAVCODEC_VERSION_MINOR  58
 #define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
-- 
2.35.1

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