1 // Copyright 2016 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef MEDIA_BASE_AUDIO_LATENCY_H_ 6 #define MEDIA_BASE_AUDIO_LATENCY_H_ 7 8 #include "media/base/media_shmem_export.h" 9 10 namespace base { 11 class TimeDelta; 12 } 13 14 namespace media { 15 16 class MEDIA_SHMEM_EXPORT AudioLatency { 17 public: 18 // Categories of expected latencies for input/output audio. Do not change 19 // existing values, they are used for UMA histogram reporting. 20 enum LatencyType { 21 // Specific latency in milliseconds. 22 LATENCY_EXACT_MS = 0, 23 // Lowest possible latency which does not cause glitches. 24 LATENCY_INTERACTIVE = 1, 25 // Latency optimized for real time communication. 26 LATENCY_RTC = 2, 27 // Latency optimized for continuous playback and power saving. 28 LATENCY_PLAYBACK = 3, 29 // For validation only. 30 LATENCY_LAST = LATENCY_PLAYBACK, 31 LATENCY_COUNT = LATENCY_LAST + 1 32 }; 33 34 // Indicates if the OS does not require resampling for playback. 35 static bool IsResamplingPassthroughSupported(LatencyType type); 36 37 // |preferred_buffer_size| should be set to 0 if a client has no preference. 38 static int GetHighLatencyBufferSize(int sample_rate, 39 int preferred_buffer_size); 40 41 // |hardware_buffer_size| should be set to 0 if unknown/invalid/not preferred. 42 static int GetRtcBufferSize(int sample_rate, int hardware_buffer_size); 43 44 static int GetInteractiveBufferSize(int hardware_buffer_size); 45 46 // Return the closest buffer size for this platform that will result in a 47 // latency not less than |duration| for the given |sample_rate|. 48 // 49 // Requirements: 50 // - |hardware_buffer_size| > 0 and |max_allowed_buffer_size| > 0. 51 // - If |min_hardware_buffer_size| and |max_hardware_buffer_size| are > 0 then 52 // the following must be true: |min_hardware_buffer_size| <= 53 // |hardware_buffer_size| <= |max_hardware_buffer_size| <= 54 // |max_allowed_buffer_size|. 55 // 56 // The returned buffer size is guaranteed to be between 57 // |min_hardware_buffer_size| and |max_allowed_buffer_size|. 58 // |max_hardware_buffer_size| is used to help determine a buffer size that 59 // won't cause the caller and the hardware to run at unsynchronized buffer 60 // sizes (e.g. hardware running at 4096 and caller running at 4224). 61 // |hardware_buffer_size| is the platform's preferred buffer size. 62 // 63 // It is valid for both the min and max to be zero in which case only 64 // |hardware_buffer_size| and multiples of it will be used. 65 static int GetExactBufferSize(base::TimeDelta duration, 66 int sample_rate, 67 int hardware_buffer_size, 68 int min_hardware_buffer_size, 69 int max_hardware_buffer_size, 70 int max_allowed_buffer_size); 71 }; 72 73 } // namespace media 74 75 #endif // MEDIA_BASE_AUDIO_LATENCY_H_ 76