IRIX Installation Tools & Overlays 1999 May

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Text File | 1999-04-19 | 14.4 KB | 397 lines

- 1 - 3. _K_n_o_w_n__P_r_o_b_l_e_m_s__a_n_d__W_o_r_k_a_r_o_u_n_d_s _M_a_x_i_m_u_m _I_m_a_g_e _S_i_z_e +o The maximum image size that OCTANE Compression or IMPACT Compression can compression or decompression in hardware is 4080 pixels wide by 4088 lines high. +o The maximum image size the scaler & color space converter hardware is capable of processing during decompression to memory or uncompressed data capture is 1024 pixels wide by 1000 lines high. Image sizes larger than this maximum are scaled and/or color space converted using software on the host CPU. _V_i_d_e_o _C_o_n_t_r_o_l _P_a_n_e_l +o In configurations without OCTANE Digital Video or IMPACT Video, the "Live Video Output" utility will fail. Without OCTANE Digital Video or IMPACT Video, OCTANE Compression and IMPACT Compression has no direct connection to the graphics subsystem, and cannot perform this operation. _C_o_m_p_r_e_s_s_i_o_n _L_i_b_r_a_r_y _I_n_t_e_r_l_e_a_v_e +o When using the interleave functionality of the compression library (CL_IMPACT_FRAME_INTERLEAVE is TRUE), the size of the uncompressed (Frame) ring buffer must be a multiple of the uncompressed, _i_n_t_e_r_l_e_a_v_e_d image size. _Y_C_r_C_b _t_o _R_G_B, _R_G_B _t_o _Y_C_r_C_b _c_o_l_o_r _c_o_n_v_e_r_s_i_o_n _i_s _n_o_t _s_y_m_m_e_t_r_i_c_a_l +o There is a difference between the two pieces of hardware that perform color space conversion on the OCTANE Compression or IMPACT Compression option. The YCrCb to RGB conversion (decompression/capture) uses one color co-siteing arrangement, while the RGB to YCrCb conversion (compression/playback) uses another. This will manifest itself as the color components of the digital video "moving" to the right in reference to the luminance when compressed/decompressed multiple times (where the uncompressed format in memory is RGBX). Workaround +o For each round-trip (compressed to decompressed to compressed), the color components will move one half - 2 - pixel to the right. For most applications this shift will be acceptable (undetectable). +o Where possible, use the YCrCb color space for uncompressed images in memory. Use software color space conversion (on the host CPU) if high quality/multiple generation compositing is to be performed. _O_u_t _o_f _R_a_n_g_e _C_o_l_o_r_s _R_e_v_e_r_s_e_d _d_u_r_i_n_g _Y_C_r_C_b _t_o _R_G_B _c_o_n_v_e_r_s_i_o_n +o During YCrCb to RGB color space conversion (optionally specified during uncompressed video capture or memory to memory decompression), out of range values may wrap. This will manifest itself through the appearance of incorrect color values in the captured data. Workaround +o If the operation is uncompressed video capture, verify that the brightness control (available on the pro panel of vcp) for the input is set to the default factory setting. Varying the brightness value may have an effect on the degree of failure. +o To avoid the problem completely, the application can capture the data to memory in the YCrCb colorspace and convert to RGB on the host CPU. _H_a_r_d_w_a_r_e _I_n_i_t_i_a_l_i_z_a_t_i_o_n _o_n _F_i_r_s_t _U_s_e +o The first use of any portion of the OCTANE Compression or IMPACT Compression board will trigger the initialization of the hardware. This initialization requires the down-load and startup of microcode, and may take up to thirty (30) seconds to complete. The requested processing will begin as soon as the initialization of the hardware has completed. Workaround +o The system administrator may configure the system to start the video daemon automatically upon system boot. This will have the effect of performing an operation on OCTANE Compression or IMPACT Compression, and the hardware will be initialized. Use the command "chkconfig videod on" to effect this change. - 3 - _A_n_a_l_o_g _V_i_d_e_o _I_n_p_u_t _c_o_n_s_i_d_e_r_a_t_i_o_n_s _w_i_t_h _O_C_T_A_N_E _D_i_g_i_t_a_l _V_i_d_e_o _o_r _I_M_P_A_C_T _V_i_d_e_o +o To fully utilize the functionality of OCTANE Digital Video or IMPACT Video with the analog video source of OCTAME Compression or IMPACT Compression, all inputs to both OCTANE Digital Video/IMPACT Video and OCTANE Compressoin/IMPACT Compression must be locked together, and the Input Autophaser should have the value "normal". _c_l_G_e_t_N_e_x_t_I_m_a_g_e_I_n_f_o() _S_t_a_t_u_s _I_n_f_o_r_m_a_t_i_o_n +o The information returned in the _s_t_a_t_u_s element of the CLimageInfo structure returned by the clGetNextImageInfo() call is incorrect. At present, the status tracks the imagecount field, and does not derive the odd/even attributes from the video input. This bug will be addressed in a future software release. _C_o_m_p_r_e_s_s_e_d, _V_e_r_t_i_c_a_l_l_y _D_e_c_i_m_a_t_e_d _I_m_a_g_e_s +o Images captured using the one half vertical decimation mode (for example, using the halfy option of dmrecord) may be of poor quality. The algorithm for reducing the number of lines of video data is straight decimation, and operates in such a way that when fields are viewed as a frame, pairs of adjacent lines have been discarded. Generally, better image quality will result through the use of lower JPEG quality factor values than will be seen by using either the one half vertical or one half horizontal decimation modes. _T_r_i_g_g_e_r _i_s _N_o_t _S_u_p_p_o_r_t_e_d +o The trigger functionality of the OCTANE Compression and IMPACT Compression is not supported in this release. This deficiency will be addressed in a future software release. _S_q_u_a_r_e _P_i_x_e_l _V_i_d_e_o _F_o_r_m_a_t _C_o_n_s_i_d_e_r_a_t_i_o_n_s +o Square pixel NTSC & PAL video formats are not supported timings in the 601 specification. As such, it is improper to generate these timings on an OCTANE Compression or IMPACT Compression and send them out the - 4 - digital ports of OCTANE Digital Video or IMPACT Video. +o The square pixel timings are not native timing formats of either OCTANE Digital Video or IMPACT Video, and may cause unexpected results. _F_a_i_l_u_r_e _t_o _C_o_m_p_i_l_e _E_x_a_m_p_l_e _C_o_d_e +o In order to compile the example code provided, the IRIS Developer's Option, Digital Media Development Environment, 6.5 (dmedia_dev), needs to have been installed on the system. _C_a_p_t_u_r_e _T_o_o_l _C_o_n_s_i_d_e_r_a_t_i_o_n_s +o When running on a system that does not have either OCTANE Digital Video or IMPACT Video installed, the capture tool will utilize both channels of the OCTANE Compression or IMPACT Compression board. This is a limitation of the capture application. +o The Compression selection on the "Settings ..." dialog of Capture will reset to "SGI Movie 2 [MVC2]" each time the settings dialog is opened. _D_m_p_l_a_y _T_o_o_l _C_o_n_s_i_d_e_r_a_t_i_o_n_s +o When used with either an OCTANE Digital Video or IMPACT Video board, the dmplay tool may not place the video output window appropriately on the graphics monitor, and if there are other video applications running, conflict with those applications. _V_i_d_e_o _a_n_d _C_o_m_p_r_e_s_s_i_o_n _S_i_z_e _R_e_q_u_i_r_e_m_e_n_t_s +o When programming OCTANE Compression or IMPACT Compression for capture or playback of compressed data from/to video, be sure that the uncompressed size of the image (CL_IMAGE_WIDTH and CL_IMAGE_HEIGHT) match the size set on the VL_CODEC node for the VL_SIZE parameter. If the sizes are not the same, unexpected results (such as channel hangs) may occur. _c_l_C_o_m_p_r_e_s_s_I_m_a_g_e +o The Compression Library call _c_l_C_o_m_p_r_e_s_s_I_m_a_g_e() is not supported on OCTANE Compression or IMPACT Compression. The issue is that there is no way to specify to the - 5 - underlying routines the size of the compressed data buffer. _A_s_y_n_c_h_r_o_n_o_u_s _S_t_o_p _C_o_n_s_i_d_e_r_a_t_i_o_n_s +o When an application sets the CL_IMPACT_CODEC_CONTROL parameter with the value CL_IMPACT_STOP, the application is required to close and re-open the codec if it wishes to perform compression or decompression operations again. _C_o_m_p_r_e_s_s_i_o_n _L_i_b_r_a_r_y _B_u_f_f_e_r _C_o_n_s_i_d_e_r_a_t_i_o_n_s +o Applications should use the _c_l_C_r_e_a_t_e_B_u_f() routine to create buffers for use with OCTANE Compression or IMPACT Compression. This routine ensures that the data buffer is page aligned, and is padded to at least a cache line boundary at the end to ensure that no cache lines are shared. If an application must use buffers that are not allocated using clCreateBuf(), they should make every attempt to ensure that the start of the data is page aligned and is a multiple of 512 bytes in length. Applications may use _m_e_m_a_l_i_g_n( _1_6_3_8_4, _s_i_z_e ) to allocate page aligned buffers. If an application is not able to use clCreateBuf(), unexpected results (channel hangs or corrupted data) may occur if a cache line is shared between the data buffer and some other variable. _L_o_w _D_a_t_a _C_o_m_p_r_e_s_s_i_o_n _R_a_t_i_o _C_o_n_s_i_d_e_r_a_t_i_o_n_s +o As the compression ratio decreases, the bandwidth to the ultimate target device increases. Most disks standard on the Indigo2 platform are able to handle a 7:1 compressed data stream to disk using the dmrecord & dmplay applets. For lower compression ratios, it is necessary to move to striped xlv volumes. Striped xlv volumes enables higher bandwidth by fanning the data flow to different disks concurrently. For higher bandwidths, balance the disks between the internal and external SCSI busses of the Indigo2 system. An example system that was using during IMPACT Compression development was a 250MHz R4400 processor with 128MB RAM and two Quantum XP32150 2GB drives. One drive was installed internally, the other externally. - 6 - By setting up a single striped xlv volume on these two disks, dmrecord and dmplay were able to sustain 4:1 compressed video with 48KHz audio to disk. To achieve 2:1 compressed data streams to disk, at least one additional hard disk is required, and a change in the programming model used to get the data to disk. See the applets _c_o_m_p_t_o_d_s_k and _d_s_k_t_o_d_e_c_o_m_p in /usr/people/4Dgifts/examples/dmedia/compression/impact/comptodsk for an example of how to get 2:1 compressed data to disk. _B_i_t_r_a_t_e _a_n_d _A_c_h_i_e_v_e_d _C_o_m_p_r_e_s_s_i_o_n _R_a_t_i_o +o In some cases of very low compression ratios (4:1 and less), developers my notice that the actual achieved compression ratio may be less than the target they had provided. This can occur when the data is easily processed by the JPEG algorithm, and the co-efficient scale values are all 1's. Essentially the Discrete Cosine Transform step of the JPEG algorithm didn't find much high frequency transitions to encode. This effect is easily seen by compressing a single color image with high bitrate values. _C_L__B_I_T_R_A_T_E _a_n_d _C_L__J_P_E_G__Q_U_A_L_I_T_Y__F_A_C_T_O_R _I_n_t_e_r_a_c_t_i_o_n +o When both CL_BITRATE and CL_JPEG_QUALITY_FACTOR are provided to the compression library, the quantization tables of the first compressed image are based on CL_JPEG_QUALITY_FACTOR. For all subsequent images, the quantization tables will be based upon the value of CL_BITRATE.