add channels option to decoder

Author: gBillal

c_src/xav/decoder.c

@@ -13,7 +13,7 @@ struct Decoder *decoder_alloc() {
   return decoder;
 }
 
-int decoder_init(struct Decoder *decoder, const AVCodec *codec) {
+int decoder_init(struct Decoder *decoder, const AVCodec *codec, int channels) {
   decoder->media_type = codec->type;
   decoder->codec = codec;
 
@@ -22,6 +22,10 @@ int decoder_init(struct Decoder *decoder, const AVCodec *codec) {
     return -1;
   }
 
+  if (codec->type == AVMEDIA_TYPE_AUDIO && channels != -1) {
+    decoder->c->channels = channels;
+  }
+
   decoder->frame = av_frame_alloc();
   if (!decoder->frame) {
     return -1;
@@ -32,11 +36,7 @@ int decoder_init(struct Decoder *decoder, const AVCodec *codec) {
     return -1;
   }
 
-  if (avcodec_open2(decoder->c, decoder->codec, NULL) < 0) {
-    return -1;
-  }
-
-  return 0;
+  return avcodec_open2(decoder->c, decoder->codec, NULL);
 }
 
 int decoder_decode(struct Decoder *decoder, AVPacket *pkt, AVFrame *frame) {

c_src/xav/decoder.h

@@ -16,7 +16,7 @@ struct Decoder {
 
 struct Decoder *decoder_alloc();
 
-int decoder_init(struct Decoder *decoder, const AVCodec *codec);
+int decoder_init(struct Decoder *decoder, const AVCodec *codec, int channels);
 
 int decoder_decode(struct Decoder *decoder, AVPacket *pkt, AVFrame *frame);
 

c_src/xav/xav_decoder.c

@@ -13,13 +13,14 @@ void free_frames(AVFrame **frames, int size) {
 }
 
 ERL_NIF_TERM new (ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
-  if (argc != 6) {
+  if (argc != 7) {
     return xav_nif_raise(env, "invalid_arg_count");
   }
 
   ERL_NIF_TERM ret;
   char *codec_name = NULL;
   char *out_format = NULL;
+  int channels;
 
   // resolve codec
   if (!xav_nif_get_atom(env, argv[0], &codec_name)) {
@@ -37,8 +38,13 @@ ERL_NIF_TERM new (ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
     goto clean;
   }
 
+  if (!enif_get_int(env, argv[1], &channels)) {
+    ret = xav_nif_raise(env, "failed_to_get_int");
+    goto clean;
+  }
+
   // resolve output format
-  if (!xav_nif_get_atom(env, argv[1], &out_format)) {
+  if (!xav_nif_get_atom(env, argv[2], &out_format)) {
     ret = xav_nif_raise(env, "failed_to_get_atom");
     goto clean;
   }
@@ -61,25 +67,25 @@ ERL_NIF_TERM new (ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
 
   // resolve other params
   int out_sample_rate;
-  if (!enif_get_int(env, argv[2], &out_sample_rate)) {
+  if (!enif_get_int(env, argv[3], &out_sample_rate)) {
     ret = xav_nif_raise(env, "invalid_out_sample_rate");
     goto clean;
   }
 
   int out_channels;
-  if (!enif_get_int(env, argv[3], &out_channels)) {
+  if (!enif_get_int(env, argv[4], &out_channels)) {
     ret = xav_nif_raise(env, "invalid_out_channels");
     goto clean;
   }
 
   int out_width;
-  if (!enif_get_int(env, argv[4], &out_width)) {
+  if (!enif_get_int(env, argv[5], &out_width)) {
     ret = xav_nif_raise(env, "failed_to_get_int");
     goto clean;
   }
 
   int out_height;
-  if (!enif_get_int(env, argv[5], &out_height)) {
+  if (!enif_get_int(env, argv[6], &out_height)) {
     ret = xav_nif_raise(env, "failed_to_get_int");
     goto clean;
   }
@@ -102,7 +108,7 @@ ERL_NIF_TERM new (ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
     goto clean;
   }
 
-  if (decoder_init(xav_decoder->decoder, codec) != 0) {
+  if (decoder_init(xav_decoder->decoder, codec, channels)) {
     ret = xav_nif_raise(env, "failed_to_init_decoder");
     goto clean;
   }
@@ -393,7 +399,7 @@ void free_xav_decoder(ErlNifEnv *env, void *obj) {
   }
 }
 
-static ErlNifFunc xav_funcs[] = {{"new", 6, new},
+static ErlNifFunc xav_funcs[] = {{"new", 7, new},
                                  {"decode", 4, decode, ERL_NIF_DIRTY_JOB_CPU_BOUND},
                                  {"flush", 1, flush, ERL_NIF_DIRTY_JOB_CPU_BOUND},
                                  {"pixel_formats", 0, pixel_formats},

lib/xav/decoder.ex

@@ -13,6 +13,14 @@ defmodule Xav.Decoder do
   @type t() :: reference()
 
   @decoder_options_schema [
+    channels: [
+      type: :pos_integer,
+      doc: """
+      The number of channels of the encoded audio.
+
+      Some decoders require this field to be set by the user. (e.g. `G711`)
+      """
+    ],
     out_format: [
       type: :atom,
       doc: """
@@ -80,6 +88,7 @@ defmodule Xav.Decoder do
 
     Xav.Decoder.NIF.new(
       codec,
+      opts[:channels] || -1,
       opts[:out_format],
       opts[:out_sample_rate] || 0,
       opts[:out_channels] || 0,

lib/xav/decoder_nif.ex

@@ -8,7 +8,15 @@ defmodule Xav.Decoder.NIF do
     :ok = :erlang.load_nif(path, 0)
   end
 
-  def new(_codec, _out_format, _out_sample_rate, _out_channels, _out_width, _out_height) do
+  def new(
+        _codec,
+        _channels,
+        _out_format,
+        _out_sample_rate,
+        _out_channels,
+        _out_width,
+        _out_height
+      ) do
     :erlang.nif_error(:undef)
   end
 

test/encoder_test.exs

@@ -124,15 +124,18 @@ defmodule Xav.EncoderTest do
         )
 
       encoded_data =
-        File.stream!(audio_file, 20)
-        |> Stream.map(&%Xav.Frame{type: :audio, data: &1, format: :s16, pts: 0})
+        File.read!(audio_file)
+        |> :binary.bin_to_list()
+        |> Enum.chunk_every(20)
+        |> Stream.map(
+          &%Xav.Frame{type: :audio, data: :binary.list_to_bin(&1), format: :s16, pts: 0}
+        )
         |> Stream.transform(
           fn -> encoder end,
           fn frame, encoder ->
             {Xav.Encoder.encode(encoder, frame), encoder}
           end,
-          fn encoder -> {Xav.Encoder.flush(encoder), encoder} end,
-          fn _encoder -> :ok end
+          fn encoder -> {Xav.Encoder.flush(encoder), encoder} end
         )
         |> Stream.map(& &1.data)
         |> Enum.join()