inptstrm.cpp

传输流分析

        DisplayInfo(" ");
        DisplayInfo("  Scanning audio stream for access units information");
        info_file = fopen (audio_units, "wb");
        if (info_file == NULL) {
                sprintf(tmpStr, "Unable to create temporary audio units file %s.", audio_units);
                DisplayInfo(tmpStr);
                return FALSE;
        }
        if (!init_getbits(&bs, audio_file))
                goto exit3;

        empty_aaunit_struc (&access_unit);

        if (!getbits(&bs, &retval, 12))
                goto exit3;

        if (retval==AUDIO_SYNCWORD) {
                if (!marker_bit(&bs, 1))
                        goto exit3;
                audio_info->num_syncword++;
                if (!getbits(&bs, &retval, 2))
                        goto exit3;
                audio_info->layer = retval;
                if (!get1bit(&bs, &retval))
                        goto exit3;
                audio_info->protection = retval;
                if (!getbits(&bs, &retval, 4))
                        goto exit3;
                audio_info->bit_rate = retval;
                if (!getbits(&bs, &retval, 2))
                        goto exit3;
                audio_info->frequency = retval;
                if (!get1bit(&bs, &retval))
                        goto exit3;
                padding_bit = retval;
                if (!get1bit(&bs, &retval))
                        goto exit3;
                if (!getbits(&bs, &retval, 2))
                        goto exit3;
                audio_info->mode = retval;
                if (!getbits(&bs, &retval, 2))
                        goto exit3;
                audio_info->mode_extension = retval;
                if (!get1bit(&bs, &retval))
                        goto exit3;
                audio_info->copyright = retval;
                if (!get1bit(&bs, &retval))
                        goto exit3;
                audio_info->original_copy = retval;
                if (!getbits(&bs, &retval, 2))
                        goto exit3;
                audio_info->emphasis = retval;

                framesize = (uint)(bitrate_index[3-audio_info->layer][audio_info->bit_rate] /
                                   frequency[audio_info->frequency] * slots [3-audio_info->layer]);
                audio_info->size_frames[0] = framesize;
                audio_info->size_frames[1] = framesize+1;

                access_unit.length = audio_info->size_frames[padding_bit];

                samples_per_second = (double)frequency [audio_info->frequency];

                PTS = decoding_order * samples [3-audio_info->layer] /
                      samples_per_second * 27000. + *startup_delay;
                make_timecode (PTS, &access_unit.PTS);
                decoding_order++;

                if (fwrite (&access_unit, sizeof (Aaunit_struc),1, info_file) != 1) {
                        sprintf(tmpStr, "Error writing to temporary audio units file %s: %s.",
                                audio_units, strerrno());
                        DisplayError(tmpStr);
                        goto exit3;
                }
                audio_count++;
                audio_info->num_frames[padding_bit]++;

                do {
                        if (AbortMPEG)
                                break;

                        percent = (int)floor(((bitcount(&bs) / 8.0)) / ((double) length) * 100.0);
                        if (percent != oldPercent) {
                                sprintf(tmpStr, "Scanning audio stream: %d%% - byte offset %.0f of %d.", percent, bitcount(&bs) / 8.0, length);
                                DisplayProgress(tmpStr, percent);
                                oldPercent = percent;
                        }

                        skip=access_unit.length-4;
                        if (skip & 0x1)
                                if (!getbits(&bs, &retval, 8))
                                        goto exit3;

                        if (skip & 0x2)
                                if (!getbits(&bs, &retval, 16))
                                        goto exit3;

                        skip = skip >> 2;

                        for (i = 0; i < skip; i++)
                                if (!getbits(&bs, &retval, 32))
                                        if (end_bs(&bs))
                                                break;
                                        else
                                                goto exit3;

                        offset_bits = bitcount(&bs);

                        if (!getbits(&bs, &retval, 12)) {
                                if (!end_bs(&bs))
                                        goto exit3;
                                else
                                        break;
                        }

                        if (retval != AUDIO_SYNCWORD) {
                                // try to find next SYNCWORD
                                u_int ret;
                                do {
                                        if (!getbits(&bs, &ret, 8))
                                                break;
                                        ;
                                        retval=(retval&0xf)<<8|ret;
                                        if (retval == AUDIO_SYNCWORD)
                                                break;
                                } while (!end_bs(&bs));
                        }

                        if (retval == AUDIO_SYNCWORD) {
                                if (!marker_bit(&bs, 1))
                                        goto exit3;
                                audio_info->num_syncword++;
                                if (!getbits(&bs, &retval, 9))
                                        goto exit3;

                                if (!get1bit(&bs, &retval))
                                        goto exit3;
                                padding_bit = retval;
                                access_unit.length = audio_info->size_frames[padding_bit];

                                PTS = decoding_order * samples [3-audio_info->layer] /
                                      samples_per_second * 27000. + *startup_delay;
                                make_timecode (PTS, &access_unit.PTS);

                                decoding_order++;

                                if (fwrite (&access_unit, sizeof (Aaunit_struc),1, info_file) != 1) {
                                        sprintf(tmpStr, "Error writing to temporary audio units file %s: %s.", audio_units, strerrno());
                                        DisplayError(tmpStr);
                                        goto exit3;
                                }
                                audio_count++;
                                audio_info->num_frames[padding_bit]++;

                                if (!getbits(&bs, &retval, 9))
                                        goto exit3;
                        } else
                                break;
                } while (!end_bs(&bs));
        } else {
                finish_getbits(&bs);
                if (!init_getbits(&bs, audio_file))
                        goto exit3;
                if (seek_sync(&bs, AC3_SYNCWORD, 16)) {
                        audio_info->layer = 0;          /* let'em know it's AC3 */
                        audio_info->num_syncword++;

                        if (!getbits(&bs, &retval, 16)) /* CRC field */
                                goto exit3;

                        if (!getbits(&bs, &retval, 2))  /* sample rate code */
                                goto exit3;
                        audio_info->frequency = retval;

                        if (!getbits(&bs, &retval, 6))  /* frame size code */
                                goto exit3;
                        framesize = ac3_frame_size[audio_info->frequency][retval >> 1];
                        if ((retval & 1) && (audio_info->frequency == 1))
                                framesize++;
                        framesize = framesize << 1;

                        audio_info->bit_rate = ac3_bitrate_index[retval >> 1];

                        audio_info->protection = 0;
                        audio_info->mode = 0;
                        audio_info->mode_extension = 0;
                        audio_info->copyright = 0;
                        audio_info->original_copy = 0;
                        audio_info->emphasis = 0;

                        audio_info->size_frames[0] = framesize;

                        access_unit.length = framesize;

                        samples_per_second = (double)ac3_frequency [audio_info->frequency];

                        PTS = decoding_order * 1536 /
                              samples_per_second * 27000. + *startup_delay;
                        make_timecode (PTS, &access_unit.PTS);
                        decoding_order++;

                        if (fwrite (&access_unit, sizeof (Aaunit_struc),1, info_file) != 1) {
                                sprintf(tmpStr, "Error writing to temporary audio units file %s: %s.",
                                        audio_units, strerrno());
                                DisplayError(tmpStr);
                                goto exit3;
                        }
                        audio_count++;
                        audio_info->num_frames[0]++;

                        do {
                                if (AbortMPEG)
                                        break;

                                percent = (int)floor(((bitcount(&bs) / 8.0)) / ((double) length) * 100.0);
                                if (percent != oldPercent) {
                                        sprintf(tmpStr, "Scanning audio stream: %d%% - byte offset %.0f of %d.", percent, bitcount(&bs) / 8.0, length);
                                        DisplayProgress(tmpStr, percent);
                                        oldPercent = percent;
                                }

                                skip = framesize - 5;
                                for (i = 0; i < skip; i++) {
                                        if (!getbits(&bs, &retval, 8))
                                                break;
                                }

                                offset_bits = bitcount(&bs);

                                if (seek_sync(&bs, AC3_SYNCWORD, 16)) {
                                        audio_info->num_syncword++;

                                        if (!getbits(&bs, &retval, 16)) /* CRC field */
                                                goto exit3;

                                        if (!getbits(&bs, &retval, 2))  /* sample rate code */
                                                goto exit3;

                                        if (!getbits(&bs, &retval, 6))  /* frame size code */
                                                goto exit3;
                                        framesize = ac3_frame_size[audio_info->frequency][retval >> 1];
                                        if ((retval & 1) && (audio_info->frequency == 1))
                                                framesize++;
                                        framesize = framesize << 1;

                                        access_unit.length = framesize;

                                        PTS = decoding_order * 1536 /
                                              samples_per_second * 27000. + *startup_delay;
                                        make_timecode (PTS, &access_unit.PTS);

                                        decoding_order++;

                                        if (fwrite (&access_unit, sizeof (Aaunit_struc),1, info_file) != 1) {
                                                sprintf(tmpStr, "Error writing to temporary audio units file %s: %s.", audio_units, strerrno());
                                                DisplayError(tmpStr);
                                                goto exit3;
                                        }
                                        audio_count++;
                                        audio_info->num_frames[0]++;
                                } else
                                        break;
                        } while (!end_bs(&bs));
                } else {
                        DisplayError("Only MPEG and AC3 audio stream formats are supported.");
                        goto exit3;
                }
        }

        if (!AbortMPEG) {
                sprintf(tmpStr, "  Found %d audio frame headers, stream bit offset %.0f.",
                        audio_info->num_syncword, offset_bits);
                DisplayInfo(tmpStr);

                audio_info->stream_length = (unsigned long) ceil(offset_bits / 8.0);
                exiterror = FALSE;
                *audio_total = audio_count;
        }

exit3:
        finish_getbits(&bs);
        fclose(info_file);
        if (exiterror)
                unlink(audio_units);
        else
                output_info_audio(audio_info);
        return !exiterror;
}