Injectable audio encoders: BuiltinAudioEncoderFactory

webrtc/modules/audio_coding/codecs/audio_encoder_factory.h

+/*
+ *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_CODING_CODECS_AUDIO_ENCODER_FACTORY_H_
+#define WEBRTC_MODULES_AUDIO_CODING_CODECS_AUDIO_ENCODER_FACTORY_H_
+
+#include <memory>
+#include <vector>
+
+#include "webrtc/api/audio_codecs/audio_format.h"
+#include "webrtc/base/refcount.h"
+#include "webrtc/modules/audio_coding/codecs/audio_encoder.h"
+
+namespace webrtc {
+
+// A factory that creates AudioEncoders.
+// NOTE: This class is still under development and may change without notice.
+class AudioEncoderFactory : public rtc::RefCountInterface {
+ public:
+  // Returns a prioritized list of audio codecs, to use for signalling etc.

[minyue-webrtc, 2017/03/23 11:36:53]

super nit: signaling.

I thought you were more American :)

[ossu, 2017/03/23 12:01:59]

I really do prefer doubling the consonant for -ing and -ed forms. We'll see if I
change it. :) 

+  virtual std::vector<AudioCodecSpec> GetSupportedEncoders() = 0;
+
+  // Returns information about how this format would be encoded, provided it's
+  // supported. More format and format variations may be supported than listed

[minyue-webrtc, 2017/03/23 11:36:53]

"listed in the list" sounds too wordy.

removing "listed" should be fine

[ossu, 2017/03/23 12:01:59]

You're right. Thanks!

+  // in the list returned by GetSupportedEncoders().
+  virtual rtc::Optional<AudioCodecInfo> QueryAudioEncoder(
+      const SdpAudioFormat& format) = 0;
+
+  // Creates an AudioEncoder for the specified format, using payload_type to
+  // identify the outputted data.

[minyue-webrtc, 2017/03/23 11:36:53]

outputted -> output

[ossu, 2017/03/23 12:01:59]

Maybe... I'm not happy with the description here, but I'm not happy about having
to provide payload_type either. I'll reconsider the wording.

[kwiberg-webrtc, 2017/03/24 12:43:25]

"It will tag the encoded payloads with the specified payload type." ?

+  // TODO(ossu): Try to avoid audio encoders having to know their payload type.

[minyue-webrtc, 2017/03/23 11:36:53]

+1

+  virtual std::unique_ptr<AudioEncoder> MakeAudioEncoder(
+      int payload_type,
+      const SdpAudioFormat& format) = 0;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_AUDIO_ENCODER_FACTORY_H_