# Basic info <!--- Add commit SHA used to reproduce--> - Float reference: - Encoder (float): 2e062fa279923ebc9b39600e34d44c36cc145de2 - Fixed point: - Encoder (fixed): 994b685932144965e2ff73e92e667127e862d60e # Bug description After doing BASOP encoder verification, it became evident that there is something causing differences in McMASA path. As MASA path (which is used for McMASA encoding) is already in relatively good shape, this suggested that the source is probably the spatial metadata estimation in `ivas_mcmasa_enc_fx`. To analyze this, introduced binary dump code at the end of the `ivas_mcmasa_enc_fx` and `ivas_mcmasa_enc` functions for variables ``` Word32 elevation_m_values_fx[MAX_PARAM_SPATIAL_SUBFRAMES][MASA_FREQUENCY_BANDS]; // Q22 Word32 azimuth_m_values_fx[MAX_PARAM_SPATIAL_SUBFRAMES][MASA_FREQUENCY_BANDS]; // Q22 Word32 energyRatio_fx[MAX_PARAM_SPATIAL_SUBFRAMES][MASA_FREQUENCY_BANDS]; // Q31 Word32 spreadCoherence_fx[MAX_PARAM_SPATIAL_SUBFRAMES][MASA_FREQUENCY_BANDS]; // Q30 Word32 surroundingCoherence_fx[MAX_PARAM_SPATIAL_SUBFRAMES][MASA_FREQUENCY_BANDS]; // Q31 ``` and float correspondents. Then I processed these in Matlab to create diff plots. The diff plot (fx-fl) for command `IVAS_cod -mc 7_1_4 96000 48 ltv48_MC714.wav out.bit` is below (Note: figure and description edited as the old figure could not be reproduced)  In this plot, negative difference is red and positive difference is green. Ideally, the plots should be completely black. Looking at the values, we have mostly small diff but highest two bands do have high estimation errors. The diff is calculated in the corresponding Q-format (i.e., float value is converted to Q-format) and the diff values are converted back to float for plotting purposes. As the spatial metadata estimation is done before any encoding, it should have maximal accuracy and it is not expected that there are very large differences between the values between fixed-point and floating point. Obviously, the quantization and encoding will reduce the accuracy of the values in the end but a lot of decisions in parameter encoding is based on the initial quantized parameter values. Thus, difference changes the bit use a lot. As a second thing, the Q-format of the values should be verified. For example, spread coherence is using Q30 whereas surround coherence is Q31. Both values should be between 0 and 1 always so difference is surprising. There is also a very peculiar line of code at line 740 of `ivas_mcmasa_enc_fx.c` ```C hQMeta->q_direction[0].band_data[i].energy_ratio_fx[j] = energyRatio_fx[k][i]; // Q30 ``` Here, the Q-format is marked as Q30. However, local value `energyRatio_fx[k][i]` has comment for Q31. The target value in band_data is Q30. Based on the values themselves, Q31 is probably correct but it would make sense to verify that this is honored everywhere. # Ways to inspect data The comparison was done by dumping for basop (at end of `ivas_mcmasa_enc_fx`) with ```C { static FILE* dumpFile = NULL; if (dumpFile == NULL) { dumpFile = fopen("./mcmasa_basop_dump.bin", "wb"); } for (i = 0; i < MAX_PARAM_SPATIAL_SUBFRAMES; i++) { fwrite(azimuth_m_values_fx[i], sizeof(Word32), MASA_FREQUENCY_BANDS, dumpFile); fwrite(elevation_m_values_fx[i], sizeof(Word32), MASA_FREQUENCY_BANDS, dumpFile); fwrite(energyRatio_fx[i], sizeof(Word32), MASA_FREQUENCY_BANDS, dumpFile); fwrite(spreadCoherence_fx[i], sizeof(Word32), MASA_FREQUENCY_BANDS, dumpFile); fwrite(surroundingCoherence_fx[i], sizeof(Word32), MASA_FREQUENCY_BANDS, dumpFile); } } ``` and for float (at end of `ivas_mcmasa_enc`) with ```C { static FILE* dumpFile = NULL; if (dumpFile == NULL) { dumpFile = fopen("./mcmasa_float_dump.bin", "wb"); } for (i = 0; i < MAX_PARAM_SPATIAL_SUBFRAMES; i++) { fwrite(azimuth_m_values[i], sizeof(float), MASA_FREQUENCY_BANDS, dumpFile); fwrite(elevation_m_values[i], sizeof(float), MASA_FREQUENCY_BANDS, dumpFile); fwrite(energyRatio[i], sizeof(float), MASA_FREQUENCY_BANDS, dumpFile); fwrite(spreadCoherence[i], sizeof(float), MASA_FREQUENCY_BANDS, dumpFile); fwrite(surroundingCoherence[i], sizeof(float), MASA_FREQUENCY_BANDS, dumpFile); } } ``` and my Matlab script for comparison (and plotting) is here [processTwoMcMASAdumps2.m](/uploads/6c6a4331408cebccdfc9b423cd323414/processTwoMcMASAdumps2.m) <!--- Below are labels that will be added but are not shown in description. This is a template to help fill them. Add further information to the first row and remove and add labels as necessary.-->