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Diffstat (limited to 'media/libstagefright/XINGSeeker.cpp')
-rw-r--r-- | media/libstagefright/XINGSeeker.cpp | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/media/libstagefright/XINGSeeker.cpp b/media/libstagefright/XINGSeeker.cpp new file mode 100644 index 0000000..72f260e --- /dev/null +++ b/media/libstagefright/XINGSeeker.cpp @@ -0,0 +1,223 @@ +/* + * Copyright (C) 2010 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#include "include/XINGSeeker.h" + +#include <media/stagefright/DataSource.h> +#include <media/stagefright/Utils.h> + +namespace android { + +static bool parse_xing_header( + const sp<DataSource> &source, off_t first_frame_pos, + int32_t *frame_number = NULL, int32_t *byte_number = NULL, + char *table_of_contents = NULL, int32_t *quality_indicator = NULL, + int64_t *duration = NULL); + +// static +sp<XINGSeeker> XINGSeeker::CreateFromSource( + const sp<DataSource> &source, off_t first_frame_pos) { + sp<XINGSeeker> seeker = new XINGSeeker; + + seeker->mFirstFramePos = first_frame_pos; + + if (!parse_xing_header( + source, first_frame_pos, + NULL, &seeker->mSizeBytes, seeker->mTableOfContents, + NULL, &seeker->mDurationUs)) { + return NULL; + } + + LOGI("Found XING header."); + + return seeker; +} + +XINGSeeker::XINGSeeker() + : mDurationUs(-1), + mSizeBytes(0) { +} + +bool XINGSeeker::getDuration(int64_t *durationUs) { + if (mDurationUs < 0) { + return false; + } + + *durationUs = mDurationUs; + + return true; +} + +bool XINGSeeker::getOffsetForTime(int64_t *timeUs, off_t *pos) { + if (mSizeBytes == 0 || mTableOfContents[0] <= 0 || mDurationUs < 0) { + return false; + } + + float percent = (float)(*timeUs) * 100 / mDurationUs; + float fx; + if( percent <= 0.0f ) { + fx = 0.0f; + } else if( percent >= 100.0f ) { + fx = 256.0f; + } else { + int a = (int)percent; + float fa, fb; + if ( a == 0 ) { + fa = 0.0f; + } else { + fa = (float)mTableOfContents[a-1]; + } + if ( a < 99 ) { + fb = (float)mTableOfContents[a]; + } else { + fb = 256.0f; + } + fx = fa + (fb-fa)*(percent-a); + } + + *pos = (int)((1.0f/256.0f)*fx*mSizeBytes) + mFirstFramePos; + + return true; +} + +static bool parse_xing_header( + const sp<DataSource> &source, off_t first_frame_pos, + int32_t *frame_number, int32_t *byte_number, + char *table_of_contents, int32_t *quality_indicator, + int64_t *duration) { + if (frame_number) { + *frame_number = 0; + } + if (byte_number) { + *byte_number = 0; + } + if (table_of_contents) { + table_of_contents[0] = 0; + } + if (quality_indicator) { + *quality_indicator = 0; + } + if (duration) { + *duration = 0; + } + + uint8_t buffer[4]; + int offset = first_frame_pos; + if (source->readAt(offset, &buffer, 4) < 4) { // get header + return false; + } + offset += 4; + + uint8_t id, layer, sr_index, mode; + layer = (buffer[1] >> 1) & 3; + id = (buffer[1] >> 3) & 3; + sr_index = (buffer[2] >> 2) & 3; + mode = (buffer[3] >> 6) & 3; + if (layer == 0) { + return false; + } + if (id == 1) { + return false; + } + if (sr_index == 3) { + return false; + } + // determine offset of XING header + if(id&1) { // mpeg1 + if (mode != 3) offset += 32; + else offset += 17; + } else { // mpeg2 + if (mode != 3) offset += 17; + else offset += 9; + } + + if (source->readAt(offset, &buffer, 4) < 4) { // XING header ID + return false; + } + offset += 4; + // Check XING ID + if ((buffer[0] != 'X') || (buffer[1] != 'i') + || (buffer[2] != 'n') || (buffer[3] != 'g')) { + if ((buffer[0] != 'I') || (buffer[1] != 'n') + || (buffer[2] != 'f') || (buffer[3] != 'o')) { + return false; + } + } + + if (source->readAt(offset, &buffer, 4) < 4) { // flags + return false; + } + offset += 4; + uint32_t flags = U32_AT(buffer); + + if (flags & 0x0001) { // Frames field is present + if (source->readAt(offset, buffer, 4) < 4) { + return false; + } + if (frame_number) { + *frame_number = U32_AT(buffer); + } + int32_t frame = U32_AT(buffer); + // Samples per Frame: 1. index = MPEG Version ID, 2. index = Layer + const int samplesPerFrames[2][3] = + { + { 384, 1152, 576 }, // MPEG 2, 2.5: layer1, layer2, layer3 + { 384, 1152, 1152 }, // MPEG 1: layer1, layer2, layer3 + }; + // sampling rates in hertz: 1. index = MPEG Version ID, 2. index = sampling rate index + const int samplingRates[4][3] = + { + { 11025, 12000, 8000, }, // MPEG 2.5 + { 0, 0, 0, }, // reserved + { 22050, 24000, 16000, }, // MPEG 2 + { 44100, 48000, 32000, } // MPEG 1 + }; + if (duration) { + *duration = (int64_t)frame * samplesPerFrames[id&1][3-layer] * 1000000LL + / samplingRates[id][sr_index]; + } + offset += 4; + } + if (flags & 0x0002) { // Bytes field is present + if (byte_number) { + if (source->readAt(offset, buffer, 4) < 4) { + return false; + } + *byte_number = U32_AT(buffer); + } + offset += 4; + } + if (flags & 0x0004) { // TOC field is present + if (table_of_contents) { + if (source->readAt(offset + 1, table_of_contents, 99) < 99) { + return false; + } + } + offset += 100; + } + if (flags & 0x0008) { // Quality indicator field is present + if (quality_indicator) { + if (source->readAt(offset, buffer, 4) < 4) { + return false; + } + *quality_indicator = U32_AT(buffer); + } + } + return true; +} + +} // namespace android + |