Yearly Archives: 2016

So manny things happened in 2016, good things, bad things, happy things, sad things, and I was busy in my own so called “The most comfortable state of mind”, but I was cheating myself actually. Now, 2017 is approaching, new year brings with it new opportunities and excuses to make […]

Saw this post on Streaming Media Magazine, found we share a same opinion with HEVC, so forward it to my blog. Online is different from broadcast and doesn’t need formal standards. HEVC isn’t considered by many online video streamers, as the future belongs to VP9 and AV1. By Jan Ozer […]

For some reason, I found out some Apps I programmed several years ago, rebuilt them and put on my MI NOTE (Android 6.0) to run some tests. Here is my cross compile environment: NDK: former downloaded, r7c + r8b SDK: newly downloaded, 24.4.1 But when I tried to run the […]

Both ZTE T800 and HUAWEI TEx0 claim to have T.140 supported, but when I digging into these entities by running some tests between T800, TE40 and TE60, my current status is I’m not persuaded. Maybe only because I don’t know how to configure them to make T.140 enabled. Here is some T.140 related information, and my steps to analysis to the protocols of HUAWEI TEx0 and ZTE T800. A screen shot of HUAWEI TEx0’s administration manual about T.140. Source: http://support.huawei.com/ehedex/pages/DOC1000063904NZD1231E/01/DOC1000063904NZD1231E/01/resources/webhlp/te_webhlp_00005.html#te_webhlp_00005__tb5 1. T.140 related standard documents 1）T-REC-H.323-200002-S!AnnG!PDF-E.pdf 2）T-REC-H.224-200501-I!!PDF-E.pdf 3）T-REC-T.140-199802-I!!PDF-E.pdf 5）T-REC-T.140-200002-I!Add1!PDF-E.pdf 6）RFC4103 – RTP Payload for Text Conversation.pdf 2. Major descriptions of implementing T.140 T.140 related descriptions in T-REC-H.323-200002-S!AnnG!PDF-E. 1) H.245 TCS for T.140 In the capabilities exchange, when using a reliable channel, specify: DataApplicationCapability.application = t140 DataProtocolCapability = tcp In the capabilities exchange, when using an unreliable channel, specify: DataApplicationCapability.application = t140 DataProtocolCapability = udp 2) H.245 Open Logical Channel In the Open Logical Channel procedure, specify: OpenLogicalChannel.forwardLogicalChannelParameters = dataType DataType = data And select a reliable or unreliable channel for the transfer of T.140 data by specifying the DataApplicationCapability and the DataProtocolCapability as above. According to the description in T-REC-H.224-200501-I!!PDF-E, there should be only one H.221 channel, we can still send multiple protocols, like FECC, T.120 and T.140, in one single channel, this type of channel has a name: H.221 MLP data channel. 3) Packetization of T.140 data Reliable TCP mode: skipped because don’t find any newlly established TCP connections. UnReliable mode: I do find an H.224 capability in both of these entities, since there is no OLC requests other than Audio, Video, and H.224 data. Let’s suppose they are re-using the H.221 MLP data channel for both FECC and T.140 transmission. 4) H.224 protocol octet structure 5) H.224 -Standard Client ID Table 3. H.224 data packets sending between TE60 and T800 I managed to extract the H.224 data packets from the PCAP file. And they are like these: 7e 7e 7e 00 86 c0 00 00 00 00 00 03 40 00 81 a8 e8 0f b2 07 db 07 9f 9f 9f bf ff Explain the packet by the standard document’s description: […]

Got mails continuously from everywhere throwing question to me about AAC audio in H.323. So I arranged this post to example my previous posts: https://oddmeta.net/archives/1480.html, https://oddmeta.net/archives/1126.html, https://oddmeta.net/archives/1112.html The pcap file for this example can be downloaded here: HUAWEI_TE600-vs-ZTE_T800.pcapnp Here it is. 1. Basic knowledge: AAC LD descriptions in 14496-3 It operates at up […]