CN103581742A - Method for converting encrypted audio stream into PCM codes on high-definition set top box - Google Patents

Method for converting encrypted audio stream into PCM codes on high-definition set top box Download PDF

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Publication number
CN103581742A
CN103581742A CN201310517855.7A CN201310517855A CN103581742A CN 103581742 A CN103581742 A CN 103581742A CN 201310517855 A CN201310517855 A CN 201310517855A CN 103581742 A CN103581742 A CN 103581742A
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CN
China
Prior art keywords
audio
audio stream
stream
pcm
video
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Pending
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CN201310517855.7A
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Chinese (zh)
Inventor
周春健
滕超
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Nanjing Panda Electronics Co Ltd
Nanjing Panda Information Industry Co Ltd
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Nanjing Panda Electronics Co Ltd
Nanjing Panda Information Industry Co Ltd
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Application filed by Nanjing Panda Electronics Co Ltd, Nanjing Panda Information Industry Co Ltd filed Critical Nanjing Panda Electronics Co Ltd
Priority to CN201310517855.7A priority Critical patent/CN103581742A/en
Publication of CN103581742A publication Critical patent/CN103581742A/en
Pending legal-status Critical Current

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Abstract

The invention provides a method for converting an encrypted audio stream into PCM codes on a high-definition set top box. The method includes the following steps that 1, before the audio stream is decoded, whether the audio stream and a video steam are synchronous or not is detected; if the audio stream and the video steam are asynchronous, a synchronous mode is adopted so as to guarantee synchronous playing of the audio stream and the video stream, and then a step 2 is performed; if the audio stream and the video steam are synchronous, the step 2 is performed directly; 2, the audio stream and the video steam are distinguished, and if the situation that the audio stream is an encrypted audio steam is found out, an encrypted audio steam conversion PCM module is started; 3, an audio decoder mode is set to be a PCM mode; 4, decryption is performed on the audio stream, the decrypted audio stream is decoded into a PCM code stream, and the PCM code stream is stored into a data buffer; 5, data are read from the data buffer and stored into an audio decoder as so to be decoded and played. The method can achieve synchronization of audio decoding and video decoding during television broadcasting, therefore, the effect that the sound of a high-definition program played by the high-definition set top box for a long time is smooth is achieved and no abnormal phenomenon occurs.

Description

On high definition set top box, realize the method for encrypted audio stream translation PCM code
Technical field
The present invention relates to digital television techniques field, in particular to a kind of method that realizes encrypted audio stream translation PCM code on high definition set top box, to realize audio decoder, synchronize with video decode.
Background technology
Nowadays, SD Set Top Box industry has developed like a raging fire, raising along with living standards of the people, SD program can not meet the needs that the common people watch HD video high quality audio, high definition set top box will be played an important role in upper once industrial upgrading. at present, country has started to play a small amount of high-definition program stream, and the appearance of high definition set top box meets a part of user and watches HDTV (High-Definition Television) demand.But As time goes on, high-definition program will occupy main status in user's life.
In high-definition data business, it is diversified that the form of audio frequency and video also becomes, video has the forms such as MPEG2, MPEG4, H264 and AVR, audio frequency has the forms such as MPEG1, MPEG2, MP3, PCM and AC3, this is just requiring us in application, for example, while cutting platform, timely switch mode, resolve different audio-video code stream.
In order to improve tonequality, at present a lot of high definition code streams, all adopt the form of encrypted audio, and adopt encrypted audio, general chip is difficult to decoding, and this gives in practical application and has brought a technical difficult problem to a certain extent.So and general television decoding chip is relatively easy to the audio stream decoding of MPEG2 and PCM form. realize encrypted audio code stream is converted into pcm stream technology, will provide huge help to the development of high definition set top box.
Summary of the invention
The object of the invention is to provide a kind of and utilizes high definition set top box to change encrypted audio circulation into pcm audio to flow to realize the method that audio decoder is synchronizeed with video decode, deposit pcm stream in audio decoder, being beneficial to audio decoder synchronizes with video decode, thereby it is smooth to realize the sound that utilizes for a long time high definition set top box to play high-definition program, without anomaly, occurs.
For reaching above-mentioned purpose, the technical solution adopted in the present invention is as follows:
Utilize high definition set top box to change encrypted audio circulation into pcm audio and flow to realize the method that audio decoder is synchronizeed with video decode, comprise the following steps:
Step 1: before decoded audio stream, whether check audio stream synchronizes with video flowing: as asynchronous, take synchronous mode to synchronize and play with video flowing to guarantee audio stream, then enter step 2; If synchronous, directly enter step 2;
Step 2: identification audio/video flow, if find that audio stream is encrypted audio stream, starts encrypted audio circulationization PCM module;
Step 3: it is PCM pattern that audio decoder pattern is set;
Step 4: audio stream is decrypted, and the audio stream after deciphering is decoded as to pcm stream and deposits data buffer zone in; And
Step 5: reading out data deposits audio decoder in the broadcasting of decoding from data buffer zone.
Further, in described step 4, the decoding of audio stream is comprised the following steps:
Step 401: decoding starts, the frame synchronization of first carrying out encrypted audio stream detects and CRC error check;
Step 402: errorless if frame synchronization detects, unpack frame head file, therefrom obtain sample rate, bit rate, coding mode and the subsequent decoding parameter of frame file;
Step 403: carry out index decoder, and the bit distribution information based on comprising in exponential sum code stream obtains the corresponding bit of each mantissa and distribute, wherein quantize mantissa and utilize corresponding bit apportioning cost solution from encrypted audio stream to press out;
Step 404: in response to having adopted couple strategy in audio stream, coupling track coefficient is arrived to each sound channel according to coupling parameter information reverting;
Step 405: in response to having used matrix replacement in audio stream, carry out matrixing processing, judge coding according to this restructuring matrix sign during decoding; And
Step 406: encrypted audio stream completes frequency domain to time domain transformation of coefficient by synthesis filter, obtains PCM signal.
From the above technical solution of the present invention shows that, beneficial effect of the present invention is to utilize high definition digital set top box to convert in real time encrypted audio code stream to pcm stream, then deposit pcm stream in audio decoder, being beneficial to audio decoder synchronizes with video decode, thereby it is smooth to realize the sound that utilizes for a long time high definition set top box to play high-definition program, without anomaly, occurs.
Accompanying drawing explanation
Fig. 1 is that the present invention utilizes high definition set top box to change encrypted audio circulation into flow chart that pcm audio flows to realize the method that audio decoder synchronizes with video decode.
Fig. 2 is the principle schematic of encrypted audio stream translation PCM module.
Embodiment
In order more to understand technology contents of the present invention, especially exemplified by specific embodiment and coordinate appended graphic being described as follows.
As shown in Figure 1, generally, behind user's opening operation interface, select to support encrypted audio stream decoding process, can utilize the method for the present embodiment to realize the synchronous of audio decoder and video decode.As shown in Figure 1-2, according to preferred embodiment of the present invention, utilize high definition set top box to change encrypted audio circulation into pcm audio and flow to realize the method that audio decoder is synchronizeed with video decode, comprise the following steps:
Step 1: before decoded audio stream, whether check audio stream synchronizes with video flowing (check system: judge that synchronous means are to see that the PCR of audio frequency and the PCR difference of video are within limits): as asynchronous, take synchronous mode (synchronous mode is known technology) to synchronize and play with video flowing to guarantee audio stream, then enter step 2; If synchronous, directly enter step 2;
Step 2: identification audio/video flow (referring to audio stream and video flowing), if find that audio stream is encrypted audio stream, starts encrypted audio circulationization PCM module;
Step 3: it is PCM pattern that audio decoder pattern is set;
Step 4: audio stream is decrypted, and the audio stream after deciphering is decoded as to pcm stream and deposits data buffer zone in; And
Step 5: reading out data deposits audio decoder in the broadcasting of decoding from data buffer zone.
Encrypted audio circulationization PCM module, audio decoder, data buffer area, synthesis filter are all arranged on realizing by software approach in high definition set top box, and prior art realizes.
Shown in figure 2, wherein, the decoding to audio stream in above-mentioned steps 4 comprises the following steps:
Step 401: decoding starts, the frame synchronization of first carrying out encrypted audio stream detects and CRC error check;
Step 402: errorless if frame synchronization detects, unpack frame head file, therefrom obtain sample rate, bit rate, coding mode and the subsequent decoding parameter of frame file, the index that subsequent decoding parameter comprises packing and the mantissa that quantizes packing;
Step 403: carry out index decoder, and the bit distribution information based on comprising in exponential sum code stream obtains the corresponding bit distribution of each mantissa, (obtain bit apportioning cost corresponding to each mantissa: according to the index policy information obtaining in code stream, index number decode index the more common corresponding bit apportioning cost of units of haunting of calculating of the bit distribution information comprising in exponential sum code stream; The mantissa here refers to quantize mantissa) wherein quantize mantissa and utilize corresponding bit apportioning cost solution from encrypted audio stream to press out;
Step 404: in response to having adopted couple strategy in audio stream, by coupling track coefficient according to coupling parameter information reverting to each sound channel (method of reducing is according to the coupling coefficient of each subband in coupling track and is coupled in sound channel the exponential sum mantissa that corresponding coupling coordinate obtains being coupled sound channel);
Step 405: in response to having used matrix replacement in audio stream, obtain restructuring matrix sign thereby carry out matrixing processing, judge coding according to this restructuring matrix sign during decoding;
Step 406: in response to step 404 and 405, encrypted audio stream completes frequency domain to time domain transformation of coefficient by synthesis filter, obtains PCM signal.
In sum, of the present inventionly utilize high definition set top box to change encrypted audio circulation into pcm audio to flow to realize the method that audio decoder is synchronizeed with video decode, utilize high definition digital set top box to convert in real time encrypted audio code stream to pcm stream, then deposit pcm stream in audio decoder, being beneficial to audio decoder synchronizes with video decode, thereby it is smooth to realize the sound that utilizes for a long time high definition set top box to play high-definition program, without anomaly, occurs.
Although the present invention discloses as above with preferred embodiment, so it is not in order to limit the present invention.Persond having ordinary knowledge in the technical field of the present invention, without departing from the spirit and scope of the present invention, when being used for a variety of modifications and variations.Therefore, protection scope of the present invention is when being as the criterion depending on claims person of defining.

Claims (4)

1. utilize high definition set top box to change encrypted audio circulation into pcm audio and flow to realize the method that audio decoder is synchronizeed with video decode, it is characterized in that, comprise the following steps:
Step 1: before decoded audio stream, whether check audio stream synchronizes with video flowing: as asynchronous, take synchronous mode to synchronize and play with video flowing to guarantee audio stream, then enter step 2; If synchronous, directly enter step 2;
Step 2: identification audio/video flow, if find that audio stream is encrypted audio stream, starts encrypted audio circulationization PCM module;
Step 3: it is PCM pattern that audio decoder pattern is set;
Step 4: audio stream is decrypted, and the audio stream after deciphering is decoded as to pcm stream and deposits data buffer zone in; And
Step 5: reading out data deposits audio decoder in the broadcasting of decoding from data buffer zone.
2. according to claim 1ly utilize high definition set top box to change encrypted audio circulation into pcm audio to flow to realize the method that audio decoder is synchronizeed with video decode, it is characterized in that, the decoding to audio stream in described step 4 comprises the following steps:
Step 401: decoding starts, the frame synchronization of first carrying out encrypted audio stream detects and CRC error check;
Step 402: errorless if frame synchronization detects, unpack frame head file, therefrom obtain sample rate, bit rate, coding mode and the subsequent decoding parameter of frame file;
Step 403: carry out index decoder, and the bit distribution information based on comprising in exponential sum code stream obtains the corresponding bit of each mantissa and distribute, wherein quantize mantissa and utilize corresponding bit apportioning cost solution from encrypted audio stream to press out;
Step 404: in response to having adopted couple strategy in audio stream, coupling track coefficient is arrived to each sound channel according to coupling parameter information reverting;
Step 405: in response to having used matrix replacement in audio stream, carry out matrixing processing, judge coding according to this restructuring matrix sign during decoding;
Step 406: and encrypted audio stream completes frequency domain to time domain transformation of coefficient by synthesis filter, obtains PCM signal.
3. according to claim 1ly utilize high definition set top box to change encrypted audio circulation into pcm audio to flow to realize the method that audio decoder is synchronizeed with video decode, it is characterized in that,
Step 1: before decoded audio stream, the check system whether check audio stream synchronizes with video flowing: judge that synchronous means are to see the PCR of audio frequency and the PCR difference of video within limits.
4. according to claim 1ly utilize high definition set top box to change encrypted audio circulation into pcm audio to flow to realize the method that audio decoder is synchronizeed with video decode, it is characterized in that,
Step 403: carry out index decoder, and the bit distribution information based on comprising in exponential sum code stream obtains the corresponding bit distribution of each mantissa, (obtain bit apportioning cost corresponding to each mantissa: according to the index policy information obtaining in code stream, index number decode index the more common corresponding bit apportioning cost of units of haunting of calculating of the bit distribution information comprising in exponential sum code stream; The mantissa here refers to quantize mantissa) wherein quantize mantissa and utilize corresponding bit apportioning cost solution from encrypted audio stream to press out;
Step 404: in response to having adopted couple strategy in audio stream, coupling track coefficient is arrived to each sound channel according to coupling parameter information reverting, and method of reducing is according to the coupling coefficient of each subband in coupling track and is coupled the exponential sum mantissa that coupling coordinate corresponding in sound channel obtains being coupled sound channel;
Step 405: in response to having used matrix replacement in audio stream, obtain restructuring matrix sign thereby carry out matrixing processing, judge coding according to this restructuring matrix sign during decoding;
Step 406: in response to step 404 and 405, encrypted audio stream completes frequency domain to time domain transformation of coefficient by synthesis filter, obtains PCM signal.
CN201310517855.7A 2013-10-28 2013-10-28 Method for converting encrypted audio stream into PCM codes on high-definition set top box Pending CN103581742A (en)

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US10791101B2 (en) * 2017-07-17 2020-09-29 Sonova Ag Encrypted audio streaming

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Patent Citations (2)

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Publication number Priority date Publication date Assignee Title
CN1777230A (en) * 2005-12-05 2006-05-24 上海广电(集团)有限公司中央研究院 Satellite digital television receiver set top box based on embedded technology
CN101188770A (en) * 2007-12-17 2008-05-28 上海广电(集团)有限公司中央研究院 An audio and video synchronization output method for multi-process control

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Application publication date: 20140212

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