HLS流媒体技术在Twitch直播平台中的实践与优化

文章对HLS流媒体技术在Twitch平台中的优化策略进行了研究。对HLS流媒体技术在实际应用中遇到的问题,如延迟、自适应码率、跨平台和跨设备兼容性、内容安全、高并发访问以及存储与传输成本等,提出了多种优化策略,并详细给出了基于机器学习的优化步骤,为解决HLS流媒体技术在Twitch平台中的自适应问题提供了可行的解决方案。

媒体融合的消费体验转向:以游戏直播网站Twitch.tv为例

Twitch.tv将消费者体验作为制胜法宝,从众多直播平台的激烈竞争中脱颖而出,其吸引消费者的举措包括体验方式上赋权消费者参与,营造数字在场感、社群共同体验感;体验效力上使消费者“卷入”媒介事件,营造“现场直播”的同感体验;体验群体上深耕频道间的融通,以聚合消费者,最大限度地吸引消费者。中国电视媒体以及媒体深度融合实践可以借鉴Twitch.tv的经验,以“消费者体验”为引擎,将“消费者体验+平台化”作为推动媒体融合向纵深发展的新思路,把分布在电视、移动终端(如手机)、桌面终端(如电脑)的不同消费者聚合起来,从而发现、锁定和货币化消费者,使媒体、消费者、赢利机会共处生态圈。

Neuromuscular fatigue and recovery profiles in individuals with intellectual disability

Purpose: This study aimed to explore neuromuscular fatigue and recovery profiles im individuals with intellectual disability(ID) after exhausting submaximal contraction.Methods: Ten men with ID were compared to 10 men without ID. The evaluation of neuromuscular function consisted in brief(3 s) isometric maximal voluntary contraction(IMVC) of the knee extension superimposed with electrical nerve stimulation before, immediately after, and during33 min after an exhausting submaximal isometric task at 15% of the IMVC. Force, voluntary activation level(VAL), potentiated twitch(Ptw), and electromyography(EMG) signals were measured during IMVC and then analyzed.Results: Individuals with ID developed lower baseline IMVC, VAL, Ptw; and RMS/M_(max) ratio(root-mean-square value normalized to the maximal peak-to-peak amplitude of the M-wave) than controls(p < 0.05). Nevertheless, the time to task failure was significantly longer in ID vs. controls(p < 0.05). The 2 groups presented similar IMVC decline and recovery kinetics after the fatiguing exercise. However. individuals with ID presented higher VAL and RMS/M_(max) ratio declines but lower Ptw decline compared to those without ID. Moreover, individuals with ID demonstrated a persistent central fatigue but faster recovery from peripheral fatigue.Conclusion: These differences in neuromuscular fatigue profiles and recovery kinetics should be acknowledged when prescribing training programs for individuals with ID.

Estimates of voluntary activation in individuals with anterior cruciate ligament reconstruction:Effects of type of stimulator,number of stimuli,and quantification technique

Background:Accurate quantification of voluntary activation is important for understanding the extent of quadriceps dysfunction in individuals with anterior cruciate ligament reconstruction(ACLR).Voluntary activation has been quantified using both percent activation derived from the interpolated twitch technique and central activation ratio(CAR)derived from the burst superimposition technique,as well as by using different types of electrical stimulators and pulse train conditions.However,it is unclear how these parameters affect voluntary activation estimates in individuals with ACLR.This study was performed to fill this important knowledge gap in the anterior cruciate ligament literature.Methods:Quadriceps strength and voluntary activation were examined in 18 ACLR participants(12 quadriceps/patellartendon graft,6 hamstring tendon graft;time since ACLR:1.06±0.82 years,mean±SD)at 90°of knee flexion using 2 stimulators(Digitimer and Grass)and pulse train conditions(3-pulse and 10-pulse).Voluntary activation was quantified by calculating both CAR and percent activation.Results:Results indicated that voluntary activation was significantly overestimated by CAR when compared with percent activation(p<0.001).Voluntary activation estimates were not affected by pulse train conditions when using percent activation;however,3-pulse stimuli resulted in greater overestimation than 10-pulse stimuli when using CAR(p=0.003).Voluntary activation did not differ between stimulators(p>0.05);however,the Digitimer evoked greater torque at rest than the Grass(p<0.001).Conclusion:These results indicate that percent activation derived from the interpolated twitch technique provides superior estimates of voluntary activation than CAR derived from burst superimposition and is less affected by pulse train conditions or stimulators in individuals with ACLR.

Integrating Deep Learning and Machine Translation for Understanding Unrefined Languages

In the field of natural language processing(NLP),the advancement of neural machine translation has paved the way for cross-lingual research.Yet,most studies in NLP have evaluated the proposed language models on well-refined datasets.We investigatewhether amachine translation approach is suitable for multilingual analysis of unrefined datasets,particularly,chat messages in Twitch.In order to address it,we collected the dataset,which included 7,066,854 and 3,365,569 chat messages from English and Korean streams,respectively.We employed several machine learning classifiers and neural networks with two different types of embedding:word-sequence embedding and the final layer of a pre-trained language model.The results of the employed models indicate that the accuracy difference between English,and English to Korean was relatively high,ranging from 3%to 12%.For Korean data(Korean,and Korean to English),it ranged from 0%to 2%.Therefore,the results imply that translation from a low-resource language(e.g.,Korean)into a high-resource language(e.g.,English)shows higher performance,in contrast to vice versa.Several implications and limitations of the presented results are also discussed.For instance,we suggest the feasibility of translation from resource-poor languages for using the tools of resource-rich languages in further analysis.

Comparison of the Analgesic Activity of Antiparkinsonian Aminoadamantane Derivatives Amantadine and Hemantane

The efficacy of some aminoadamantane derivatives used as neurodegeneration treatments is due to their ability to block NMDA receptors. But this mechanism of pharmacological action can also produce analgesic activity. Analgesic properties of two aminoadamantanes, amantadine (20 mg/kg) and hemantane (20 mg/kg), which were uncompetitive NMDA receptor antagonists, were assessed in rodent models of pain induced by different pain stimuli (tail-flick test, acetic twitches test in mice and formalin test in rats). Additionally, the anti-inflammatory properties of hemantane and amantadine were evaluated in mice with acetic peritonitis and in rats with hind paw edema induced by formalin injection. The results of our study demonstrate that the analgesic activity of the 1-aminoadamantane amantadine differs from the 2-aminoadamantane hemantane. The analgesic activity of amantadine administered intraperitoneally was more pronounced in the case of acute thermal pain in mice compared to hemantane, and only amantadine had a significant analgesic effect on the acute early phase of formalin pain in rats induced by the effect of the algogen on the primary sensory afferents. Hemantane was more effective than amantadine for relieving pain produced by inflammation owing to its pronounced anti-inflammatory activity: only hemantane decreased the amount of acetic twitches in mice that received drugs orally and was effective in the tonic phase of formalin pain in rats.

电子竞技带动了Twitch平台21.3%的收视率

Tip：Twitch,面向视频游戏的实时流媒体平台,总部位于旧金山。网站支持28个国家和地区的语言,其中包括简体中文和繁体中文。创立目标是成为＂游戏界的ESPN＂。在西方,人们常说Twitch是促进电子竞技发展的真正助力器,相对也不能否认,电竞也帮助Twitch成为了现在的顶尖视频直播平台。根据Newzoo公司对Twitch的跟踪研究,从2015年7月-12月,平台观看内容的21.3%是有关电竞的。

Sex and stress modulate pupal defense response in tobacco hornworm

In insects,larval and adult defenses against predators have been well studied.However,pupal(also known as resting stage)defenses have been overlooked and not examined thoroughly.Although some pupa possess antipredator strategies such as hairs,spines,cryptic coloration,and exudation of chemicals,few studies have tested these responses and the factors affecting them.Here,we investigated the behavioral responses in tobacco hornworm Manduca sexta that pupates in soil by introducing an external stimulus using vibrations from an electric toothbrush to mimic predation.We observed that M.sexta made violent wriggling(twitching),followed by pulsating movements in response to the vibrational stimulus.Detailed examination showed that these twitches and pulsating events occurred more frequently and for longer periods of time in male pupa and were dependent on the magnitude of the stress(high and low frequency).However,when we estimated the angular force exerted by pupa using radian and angular momentum of twitches,it was found to be independent of pupal sex.A follow-up experiment on possible cascading effects of stress exposure on eclosion success revealed that low-and high-frequency stress exposure didn’t cause any of the common defects in eclosed adults.Our study clearly demonstrates that the so-called defenseless pupal stage uses a wide range of measurable defense behaviors that can actively defend against predators and should be examined further-linking observed behavior with underlying mechanisms.

DYNAMIC PROPERTIES OF ASSISTANT SOUNDER IN BLACK CICADA (C.atrata FABRICIUS)

The dynamic properties of the assistant sounders in the black cicada are given and the twitching properties of Contraction in the sounding muscle are revealed in this paper.For the operculum, tymbal cover and joint membrane, each of their vibration periods consists of three subgroup vibrations (SGV_(a,b,c)) corresponding to amplitude-modulation pulse trains (AMPT_(1,2,3)) in every syllable of synchro song. In comparison with the vibration at dorsum, the SGV_(a-c) have a subband with the function of regulating the tone. During calling song continuously, the pressure change inside the resonant cavity and the airspeed through the spiracles on both sides are about 7. 94—15.88 Paand 0.59—0.84 cm^3/s respectively, and they increase by about 7 and 2.6 times as the abdomen is moved. When the contraction motion of the sounding muscle comes up to the critical Sounding state, it further produces the twitching process, and drives the sounding membrane and the toning plate-membrane to produce AMPT_(1-3) and SGV_(a-c).

Depression of Calcium Transients After Exposure to High K^+ Solution in Li^+-loaded Frog Twitch Muscle Fibres and Its Reversal by Exogenous Myo-inositol

Using Arsenazo Ⅲ as a myoplasmic calcium indicator, we have studied the calcium transients evoked by voltage-clamp depolarizing pulses in frog twitch muscle fibres which had been temporarily depolarized by 80 mmol/LK^+ in the absence or presence of myoplasmic Li^+. After the high K^+ exposure, for either a short (15 rain) or long(1 h) time, the post-K^+ calcium transients could gradually be restored to the level of the pre-K^+ ones, if the fibres were not loaded with Li^+.In contrast, the post-K^+ calcium transients of Li^+-loaded fibres could not fully recover,and were depressed in a Li^+ concentration-dependent manner.The mean amplitude of the post-K^+ responses recorded more than 3.5 h after 15 min high K^+ exposure was reduced to 56% of pre-K^+ control in the fibres which had been loaded with Li^+ in 20 mmol/L Li^+ Ringer's solution.This depression could be prevented or partially reversed by exogenous myo-inositol.More depression could be induced by 1 h high K^+ exposure, but the presence of exogenous myo-inositol could not clearly prevent the post-K^+ calcium transients from reduction.Assuming that high K^+ exposure caused a depletion of myo-inositol and probably other changes in the metabolism of inositol phospholipids in Li^+ loaded fibres,we conclude that some metabolites of phosphoinositides may play modulation roles in excitation-contraction coupling in frog twitch muscle fibres.

Quadriceps strength assessed by magnetic stimulation of femoral nerve in patients with chronic obstructive pulmonary disease

Background Skeletal muscle dysfunction is one of important systemic manifestations of chronic obstructive pulmonary disease （COPD） and is associated with mortality in patients with COPD, thus quantifying its strength is of great clinical interest and of particular value. Quadriceps maximal volitional contraction （MVC） is often used for the routine measurements of this muscle＇s strength; while twitch tension （TwQ） evoked by magnetic stimulation of the femoral nerve has been employed for measurement of quadriceps strength non-volitionally. We aimed to investigate the prevalence and severity of skeletal muscle dysfunction in COPD patients by measurement of quadriceps strength with volitional and non-volitional techniques, and to probe into some methodological issues. Methods We recruited 71 COPD patients and 60 control subjects. Quadriceps strength was measured with both maximality of TwQ and MVC force. The reproducibility for TwQ and MVC was investigated using within-occasion variability from three repeated maneuvers. Results Maximal TwQ was achieved in 121 participants at a mean of 90% of the stimulator＇s maximum output. The mean maxmality of TwQ was decrease by about 44%-47% in COPD patients as compared with controls （P 〈0.05）, so was MVC. There was a significant correlation between quadriceps TwQ and MVC, and the mean ratio of TwQ/MVC was 0.29 in controls and 0.33 in patients. The coefficient of variation showed that TwQ yielded lower within-occasion variability than MVC in both groups. Conclusions Quadriceps strength is commonly and substantially impaired in patients with COPD, in terms of MVC as well as TwQ. The magnetic stimulation of the femoral nerve presents a higher reproducibility and is a better technique for measurement of quadriceps strength for the general population, especially for those who are too unwell to perform a full MVC; while it may not be applied to subjects who are over-weighted.

The Effects of Short-Term Resistance Training and Subsequent Detraining on Neuromuscular Function,Muscle Cross-Sectional Area,and Lean Mass

Purpose To examine and compare the effects of three days of dynamic constant external resistance(DCER)and isokinetic(ISOK)training and subsequent detraining on thigh muscle cross-sectional area(TMCSA)and thigh lean mass(TLM),ISOK peak torque(PT),DCER strength,isometric force,muscle activation,and percent voluntary activation(%VA).Methods Thirty-one apparently-healthy untrained men(mean±SD age=22.2±4.2 years;body mass=77.9±12.9 kg;height=173.9±5.4 cm)were randomly assigned to a DCER training group(n=11),ISOK training group(n=10)or control(CONT)group(n=10).Subjects visited the laboratory eight times.The first visit was a familiarization session,the second visit was a pre-training assessment,the subsequent three visits were for unilateral training of the quadriceps(if assigned to a training group),and the last three visits were the post-training assessments conducted at three days,one week,and two weeks after training ended.Results DCER strength increased from pre-to post-training assessment 1 in both limbs for the DCER group only,and remained elevated during post-training assessments 2 and 3(P<0.05).In addition,surface EMG for the biceps femoris was higher at post-training assessment 3 than at the pre-training assessment,and post-training assessments 1 and 2(P<0.05).No other training-related changes were found.Conclusion The primary finding of this study was that DCER strength of the trained and untrained limbs can be increased with three days of training.This has important implications for injury rehabilitation,where in the initial period post-injury strength gains on an injured limb can possibly be obtained with short-term contralateral resistance training.

Downhill running impairs peripheral but not central neuromuscular indices in elbow flexor muscles

The purpose of this study was to examine the effects of a 1-h downhill running exercise on the elbow flexor muscles’neuromuscular functions.Seventeen adults(Control[CON]:n=9;Experimental[EXP]:n=8)completed this study.The CON rested for 30 min while the EXP performed the downhill running.Before,10 min,24 h,and 48 h after the interventions,dependent variables(knee extensor muscle soreness,elbow flexion and knee extension isometric strength,elbow flexion resting twitch and voluntary activation[VA],and the biceps surface electromyography[EMG]amplitude)were measured.Knee extensor muscle soreness was significantly greater in the EXP than the CON group following the intervention throughout the entire 48 h.This was accompanied by the greater decline in the knee extension strength in the EXP than the CON(mean±SD:-6.9±3.4%vs.1.0±3.2%,p=0.044).The elbow flexion strength,VA,and EMG amplitude were not affected by the exercise.However,the decline of the elbow flexion resting twitch was greater in the EXP than the CON(±19.6±6.3%vs.8.7±5.9%,p=0.003).Therefore,the downhill running impaired the remote elbow flexor muscles at a peripheral level.