Re: [FFmpeg-devel] [PATCH v2 1/2] libavcodec: Added DFPWM1a codec

[Jack Bruienne <jackbruienne@gmail.com>]

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Sorry, I forgot to run make fate on the split patches, and I used the 
wrong capabilities for the decoder. I have attached a modified patch 
that removes AV_CODEC_CAP_VARIABLE_FRAME_SIZE from the decoder 
capabilities. Let me know if you'd like a full v3 patch email instead.

On 2/25/22 18:43, Jack Bruienne wrote:
>
> From the wiki page (https://wiki.vexatos.com/dfpwm):
>> DFPWM (Dynamic Filter Pulse Width Modulation) is an audio codec
>> created by Ben “GreaseMonkey” Russell in 2012, originally to be used
>> as a voice codec for asiekierka's pixmess, a C remake of 64pixels.
>> It is a 1-bit-per-sample codec which uses a dynamic-strength one-pole
>> low-pass filter as a predictor. Due to the fact that a raw DPFWM 
>> decoding
>> creates a high-pitched whine, it is often followed by some 
>> post-processing
>> filters to make the stream more listenable.
>
> It has recently gained popularity through the ComputerCraft mod for
> Minecraft, which added support for audio through this codec, as well as
> the Computronics expansion which preceeded the official support. These
> both implement the slightly adjusted 1a version of the codec, which is
> the version I have chosen for this patch.
>
> This patch adds a new codec (with encoding and decoding) for DFPWM1a.
>
> The codec sources are pretty simple: they use the reference codec with
> a basic wrapper to connect it to the FFmpeg AVCodec system.
>
> This patch will be highly useful to ComputerCraft developers who are
> working with audio, as it is the standard format for audio, and there
> are few user-friendly encoders out there. It will streamline the process
> for importing audio, replacing the need to write code or use tools that
> require very specific input formats.
>
> You may use the CraftOS-PC program (https://www.craftos-pc.cc) to test
> out DFPWM playback. To use it, run the program and type this command:
> "attach left speaker" Then run "speaker play <file.dfpwm>" for each file.
> The app runs in a sandbox, so files have to be transferred in first;
> the easiest way to do this is to simply drag the file on the window.
> (Or copy files to the folder at https://www.craftos-pc.cc/docs/saves.)
>
> Sample DFPWM files can be generated with an online tool at
> https://music.madefor.cc. This is the current best way to encode DFPWM
> files. Simply drag an audio file onto the page, and it will encode it,
> giving a download link on the page.
>
> I've made sure to update all of the docs as per Developer§7, and I've
> tested it as per section 8. Test files encoded to DFPWM play correctly
> in ComputerCraft, and other files that work in CC are correctly decoded.
> I have also verified that corrupt files do not crash the decoder - this
> should theoretically not be an issue as the result size is constant with
> respect to the input size.
>
> Signed-off-by: Jack Bruienne <jackbruienne@gmail.com>
> ---
>  Changelog                 |   1 +
>  MAINTAINERS               |   1 +
>  doc/general_contents.texi |   1 +
>  libavcodec/Makefile       |   2 +
>  libavcodec/allcodecs.c    |   2 +
>  libavcodec/codec_desc.c   |   7 +++
>  libavcodec/codec_id.h     |   1 +
>  libavcodec/dfpwmdec.c     | 129 ++++++++++++++++++++++++++++++++++++++
>  libavcodec/dfpwmenc.c     | 123 ++++++++++++++++++++++++++++++++++++
>  libavcodec/utils.c        |   2 +
>  libavcodec/version.h      |   2 +-
>  11 files changed, 270 insertions(+), 1 deletion(-)
>  create mode 100644 libavcodec/dfpwmdec.c
>  create mode 100644 libavcodec/dfpwmenc.c
>

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diff --git a/Changelog b/Changelog
index 5ad2cef..5170a6a 100644
--- a/Changelog
+++ b/Changelog
@@ -4,6 +4,7 @@ releases are sorted from youngest to oldest.
 version 5.1:
 - dialogue enhance audio filter
 - dropped obsolete XvMC hwaccel
+- DFPWM audio encoder/decoder
 
 
 version 5.0:
diff --git a/MAINTAINERS b/MAINTAINERS
index f33ccbd..57b6f33 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -161,6 +161,7 @@ Codecs:
   cscd.c                                Reimar Doeffinger
   cuviddec.c                            Timo Rothenpieler
   dca*                                  foo86
+  dfpwm*                                Jack Bruienne
   dirac*                                Rostislav Pehlivanov
   dnxhd*                                Baptiste Coudurier
   dolby_e*                              foo86
diff --git a/doc/general_contents.texi b/doc/general_contents.texi
index df1692c..14aeaed 100644
--- a/doc/general_contents.texi
+++ b/doc/general_contents.texi
@@ -1194,6 +1194,7 @@ following image formats are supported:
 @item CRI HCA                @tab     @tab X
 @item Delphine Software International CIN audio  @tab     @tab  X
     @tab Codec used in Delphine Software International games.
+@item DFPWM                  @tab  X  @tab  X
 @item Digital Speech Standard - Standard Play mode (DSS SP) @tab     @tab  X
 @item Discworld II BMV Audio @tab     @tab  X
 @item COOK                   @tab     @tab  X
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 6076b4a..7474220 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -289,6 +289,8 @@ OBJS-$(CONFIG_DERF_DPCM_DECODER)       += dpcm.o
 OBJS-$(CONFIG_DIRAC_DECODER)           += diracdec.o dirac.o diracdsp.o diractab.o \
                                           dirac_arith.o dirac_dwt.o dirac_vlc.o
 OBJS-$(CONFIG_DFA_DECODER)             += dfa.o
+OBJS-$(CONFIG_DFPWM_DECODER)           += dfpwmdec.o
+OBJS-$(CONFIG_DFPWM_ENCODER)           += dfpwmenc.o
 OBJS-$(CONFIG_DNXHD_DECODER)           += dnxhddec.o dnxhddata.o
 OBJS-$(CONFIG_DNXHD_ENCODER)           += dnxhdenc.o dnxhddata.o
 OBJS-$(CONFIG_DOLBY_E_DECODER)         += dolby_e.o dolby_e_parse.o kbdwin.o
diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
index d1e1019..c3a0c26 100644
--- a/libavcodec/allcodecs.c
+++ b/libavcodec/allcodecs.c
@@ -437,6 +437,8 @@ extern const AVCodec ff_bmv_audio_decoder;
 extern const AVCodec ff_cook_decoder;
 extern const AVCodec ff_dca_encoder;
 extern const AVCodec ff_dca_decoder;
+extern const AVCodec ff_dfpwm_encoder;
+extern const AVCodec ff_dfpwm_decoder;
 extern const AVCodec ff_dolby_e_decoder;
 extern const AVCodec ff_dsd_lsbf_decoder;
 extern const AVCodec ff_dsd_msbf_decoder;
diff --git a/libavcodec/codec_desc.c b/libavcodec/codec_desc.c
index 725c687..81f3b3c 100644
--- a/libavcodec/codec_desc.c
+++ b/libavcodec/codec_desc.c
@@ -3237,6 +3237,13 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .long_name = NULL_IF_CONFIG_SMALL("MSN Siren"),
         .props     = AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSY,
     },
+    {
+        .id        = AV_CODEC_ID_DFPWM,
+        .type      = AVMEDIA_TYPE_AUDIO,
+        .name      = "dfpwm",
+        .long_name = NULL_IF_CONFIG_SMALL("DFPWM (Dynamic Filter Pulse Width Modulation)"),
+        .props     = AV_CODEC_PROP_LOSSY,
+    },
 
     /* subtitle codecs */
     {
diff --git a/libavcodec/codec_id.h b/libavcodec/codec_id.h
index ab265ec..3ffb9bd 100644
--- a/libavcodec/codec_id.h
+++ b/libavcodec/codec_id.h
@@ -516,6 +516,7 @@ enum AVCodecID {
     AV_CODEC_ID_HCA,
     AV_CODEC_ID_FASTAUDIO,
     AV_CODEC_ID_MSNSIREN,
+    AV_CODEC_ID_DFPWM,
 
     /* subtitle codecs */
     AV_CODEC_ID_FIRST_SUBTITLE = 0x17000,          ///< A dummy ID pointing at the start of subtitle codecs.
diff --git a/libavcodec/dfpwmdec.c b/libavcodec/dfpwmdec.c
new file mode 100644
index 0000000..e157145
--- /dev/null
+++ b/libavcodec/dfpwmdec.c
@@ -0,0 +1,129 @@
+/*
+ * DFPWM decoder
+ * Copyright (c) 2022 Jack Bruienne
+ * Copyright (c) 2012, 2016 Ben "GreaseMonkey" Russell
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * DFPWM1a decoder
+ */
+
+#include "libavutil/internal.h"
+#include "avcodec.h"
+#include "codec_id.h"
+#include "internal.h"
+
+typedef struct {
+    int fq, q, s, lt;
+} DFPWMState;
+
+// DFPWM codec from https://github.com/ChenThread/dfpwm/blob/master/1a/
+// Licensed in the public domain
+
+#ifndef CONST_PREC
+#define CONST_PREC 10
+#endif
+
+static void au_decompress(DFPWMState *state, int fs, int len, uint8_t *outbuf, uint8_t *inbuf)
+{
+    int i, j;
+    uint8_t d;
+    for (i = 0; i < len; i++) {
+        // get bits
+        d = *(inbuf++);
+        for (j = 0; j < 8; j++) {
+            int nq, lq, st, ns, ov;
+            // set target
+            int t = ((d&1) ? 127 : -128);
+            d >>= 1;
+
+            // adjust charge
+            nq = state->q + ((state->s * (t-state->q) + (1<<(CONST_PREC-1)))>>CONST_PREC);
+            if(nq == state->q && nq != t)
+                state->q += (t == 127 ? 1 : -1);
+            lq = state->q;
+            state->q = nq;
+
+            // adjust strength
+            st = (t != state->lt ? 0 : (1<<CONST_PREC)-1);
+            ns = state->s;
+            if(ns != st)
+                ns += (st != 0 ? 1 : -1);
+#if CONST_PREC > 8
+            if(ns < 1+(1<<(CONST_PREC-8))) ns = 1+(1<<(CONST_PREC-8));
+#endif
+            state->s = ns;
+
+            // FILTER: perform antijerk
+            ov = (t != state->lt ? (nq+lq)>>1 : nq);
+
+            // FILTER: perform LPF
+            state->fq += ((fs*(ov-state->fq) + 0x80)>>8);
+            ov = state->fq;
+
+            // output sample
+            *(outbuf++) = ov + 128;
+
+            state->lt = t;
+        }
+    }
+}
+
+static av_cold int dfpwm_dec_init(struct AVCodecContext *ctx)
+{
+    DFPWMState *state = ctx->priv_data;
+
+    state->fq = 0;
+    state->q = 0;
+    state->s = 0;
+    state->lt = -128;
+
+    return 0;
+}
+
+static int dfpwm_dec_frame(struct AVCodecContext *ctx, void *data,
+    int *got_frame, struct AVPacket *packet)
+{
+    DFPWMState *state = ctx->priv_data;
+    AVFrame *frame = data;
+
+    frame->format = AV_SAMPLE_FMT_U8;
+    frame->nb_samples = packet->size * 8;
+    frame->channel_layout = AV_CH_LAYOUT_MONO;
+
+    ff_get_buffer(ctx, frame, 0);
+
+    au_decompress(state, 100, packet->size, frame->data[0], packet->data);
+
+    if (got_frame) *got_frame = 1;
+    return packet->size;
+}
+
+const AVCodec ff_dfpwm_decoder = {
+    .name           = "dfpwm",
+    .long_name      = NULL_IF_CONFIG_SMALL("DFPWM1a audio"),
+    .type           = AVMEDIA_TYPE_AUDIO,
+    .id             = AV_CODEC_ID_DFPWM,
+    .priv_data_size = sizeof(DFPWMState),
+    .init           = dfpwm_dec_init,
+    .decode         = dfpwm_dec_frame,
+    .capabilities   = AV_CODEC_CAP_DR1,
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
+};
\ No newline at end of file
diff --git a/libavcodec/dfpwmenc.c b/libavcodec/dfpwmenc.c
new file mode 100644
index 0000000..5fcc0c1
--- /dev/null
+++ b/libavcodec/dfpwmenc.c
@@ -0,0 +1,123 @@
+/*
+ * DFPWM encoder
+ * Copyright (c) 2022 Jack Bruienne
+ * Copyright (c) 2012, 2016 Ben "GreaseMonkey" Russell
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * DFPWM1a encoder
+ */
+
+#include "libavutil/internal.h"
+#include "avcodec.h"
+#include "codec_id.h"
+#include "internal.h"
+
+typedef struct {
+    int fq, q, s, lt;
+} DFPWMState;
+
+// DFPWM codec from https://github.com/ChenThread/dfpwm/blob/master/1a/
+// Licensed in the public domain
+
+#ifndef CONST_PREC
+#define CONST_PREC 10
+#endif
+
+// note, len denotes how many compressed bytes there are (uncompressed bytes / 8).
+static void au_compress(DFPWMState *state, int len, uint8_t *outbuf, uint8_t *inbuf)
+{
+    int i, j;
+    uint8_t d = 0;
+    for (i = 0; i < len; i++) {
+        for (j = 0; j < 8; j++) {
+            int nq, st, ns;
+            // get sample
+            int v = *(inbuf++) - 128;
+            // set bit / target
+            int t = (v < state->q || v == -128 ? -128 : 127);
+            d >>= 1;
+            if(t > 0)
+                d |= 0x80;
+
+            // adjust charge
+            nq = state->q + ((state->s * (t-state->q) + (1<<(CONST_PREC-1)))>>CONST_PREC);
+            if(nq == state->q && nq != t)
+                nq += (t == 127 ? 1 : -1);
+            state->q = nq;
+
+            // adjust strength
+            st = (t != state->lt ? 0 : (1<<CONST_PREC)-1);
+            ns = state->s;
+            if(ns != st)
+                ns += (st != 0 ? 1 : -1);
+#if CONST_PREC > 8
+            if(ns < 1+(1<<(CONST_PREC-8))) ns = 1+(1<<(CONST_PREC-8));
+#endif
+            state->s = ns;
+
+            state->lt = t;
+        }
+
+        // output bits
+        *(outbuf++) = d;
+    }
+}
+
+static av_cold int dfpwm_enc_init(struct AVCodecContext *ctx)
+{
+    DFPWMState *state = ctx->priv_data;
+
+    state->fq = 0;
+    state->q = 0;
+    state->s = 0;
+    state->lt = -128;
+
+    return 0;
+}
+
+static int dfpwm_enc_frame(struct AVCodecContext *ctx, struct AVPacket *packet,
+    const struct AVFrame *frame, int *got_packet)
+{
+    DFPWMState *state = ctx->priv_data;
+    int size = frame->nb_samples / 8 + (frame->nb_samples % 8 > 0 ? 1 : 0);
+
+    if (packet->size < size) av_grow_packet(packet, size - packet->size);
+    else if (packet->size > size) av_shrink_packet(packet, size);
+
+    au_compress(state, size, packet->data, frame->data[0]);
+
+    if (got_packet) *got_packet = 1;
+    return 0;
+}
+
+const AVCodec ff_dfpwm_encoder = {
+    .name            = "dfpwm",
+    .long_name       = NULL_IF_CONFIG_SMALL("DFPWM1a audio"),
+    .type            = AVMEDIA_TYPE_AUDIO,
+    .id              = AV_CODEC_ID_DFPWM,
+    .priv_data_size  = sizeof(DFPWMState),
+    .init            = dfpwm_enc_init,
+    .encode2         = dfpwm_enc_frame,
+    .sample_fmts     = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_U8, AV_SAMPLE_FMT_NONE},
+    .channel_layouts = (const uint64_t[]){AV_CH_LAYOUT_MONO, 0},
+    .capabilities    = AV_CODEC_CAP_VARIABLE_FRAME_SIZE,
+    .caps_internal   = FF_CODEC_CAP_INIT_THREADSAFE,
+};
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 6f9d90a..066da76 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -577,6 +577,8 @@ enum AVCodecID av_get_pcm_codec(enum AVSampleFormat fmt, int be)
 int av_get_bits_per_sample(enum AVCodecID codec_id)
 {
     switch (codec_id) {
+    case AV_CODEC_ID_DFPWM:
+        return 1;
     case AV_CODEC_ID_ADPCM_SBPRO_2:
         return 2;
     case AV_CODEC_ID_ADPCM_SBPRO_3:
diff --git a/libavcodec/version.h b/libavcodec/version.h
index d900503..84f3979 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -28,7 +28,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVCODEC_VERSION_MAJOR  59
-#define LIBAVCODEC_VERSION_MINOR  21
+#define LIBAVCODEC_VERSION_MINOR  22
 #define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \

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